Good evening,
A quote from p. 319:

Conclusion
We have seen that the giving of the Torah’s commandments through Moses at a different prophetic level is necessary in order to define them as Torah. Commands that were given to Moses in the wilderness for their own time, and do not enter the general category of the 613 commandments, did not have to be given specifically to Moses by the Holy One, blessed be He; therefore, even though Moses was the one conveying them, he could have functioned in this respect with the status of a prophet like all other prophets. 41 It is therefore clear that Maimonides’ claim is correct: regarding a temporary commandment, there is no significance to saying that it was given at Sinai, just as we do not say that Elijah received at Sinai the command to anoint Elisha, even though this was said to him at Mount Horeb, because the meaning of the statement that commandments were ‘given at Sinai’ is essential, not geographic.

This is not about Moses’ level of prophecy. It could have been given through a prophet lesser than him, but in practice it was given through him.
As for your question, yes, that is correct. It is a prophet’s temporary directive.

The Halakhot Gedolot counted the Hanukkah candle as part of the 613 commandments. Maimonides, in the first root at the opening of Sefer HaMitzvot, challenged this and argued that the commandment of the Hanukkah candle is rabbinic, and one cannot count rabbinic commandments among the 613, because they were not said at Sinai. Nor can one say that the commandment of the Hanukkah candle is from the Torah, because it is inconceivable that Moses was commanded at Sinai that a thousand years later there would be a war with the Greeks and there would be an obligation to light the Hanukkah candle.

That is, it is impossible that we were commanded regarding a commandment dependent on a historical event when that historical event had not yet occurred.
In the third root, Maimonides determined that temporary commandments are not to be counted as part of the 613. Maimonides explains that the 613 commandments were given at Sinai, and those commandments that are not permanent were not given specifically at Sinai. For example, the commandment that an heiress must marry a son of her tribe was given at the end of the forty years.

In the portion of Ki Tetze, the Torah explains the prohibition, “An Ammonite or Moabite shall not enter the congregation of the Lord”: “Because they did not meet you with bread and with water on the way, when you came forth out of Egypt; and because they hired against you Balaam the son of Beor from Pethor of Aram-Naharaim to curse you.”

Maimonides counted this as prohibition 53. Was this commandment given at Sinai? According to the first rule, it cannot have been given at Sinai, since the event of Balaam was at the end of the forty years, and it is impossible to make a commandment depend on an event that had not yet happened. On the other hand, if it was not given at Sinai, it cannot be counted as part of the 613?

Let me begin by noting that there are commandments that were given to us before Sinai, and Maimonides relates to them as though they were given at Sinai. That is true of the prohibition of the sciatic nerve as well—his comments in his commentary on the Mishnah, at the end of the seventh chapter of Hullin, are well known. The same applies to what was given afterward, so long as it is written in the Torah. For Maimonides, whatever is written in the Torah is considered as having been given at Sinai.
Your question is not essentially different from the question of how the entire Torah was given at Sinai if it describes events that took place after the revelation at Mount Sinai. Especially since, as is well known, Rabbi Akiva and Rabbi Ishmael disagreed whether the Torah was given scroll by scroll, in the Tent of Meeting, or at Mount Sinai—its general principles or its details. And there too there is no contradiction to saying that everything was said at Sinai, because whatever appears in the Torah and was written by Moses is considered as though it was given at Sinai.
The Vilna Gaon said that the entire Torah was given at Sinai in a mixed-up form, and after a given event occurred, the letters were arranged by Moses our Rabbi and the text familiar to us today was formed. What distinguishes the last eight verses is that the one who arranged the letters was not Moses but Joshua. Moses wrote in a tearful state. This is a description that seemingly puts things into a historical framework, but I’m not sure one has to go that far. As I said, even if the Torah was given to Moses scroll by scroll, everything that appears in the Torah is considered as if it was given at Sinai.
Of course, regarding Hanukkah and Purim, there was no one who would arrange things in that way, so that solution does not exist.
As for Maimonides’ own difficulty, it is of course fairly weak. The Torah does not need to tell us that there will be Greeks and that we will defeat them; it only needs to establish the principle that after a victory there is an obligation to remember it and celebrate it, while the sages determine the format. Something like what people cite from Meiri regarding Independence Day. And perhaps that option was difficult for him, because if so, Hanukkah and Purim should not be counted separately but as one general commandment.