Question

Good evening, Rabbi Michi,
Festive greetings.
Recently I came across what Maimonides wrote in the Laws of Eruvin, chapter 2, halakhah 16:
“A Jew who publicly desecrates the Sabbath, or who worships stars and constellations, is like an idolater in every respect… But if he is among the heretics who do not worship stars and constellations and do not desecrate the Sabbath, such as the Sadducees and Boethusians and all who deny the Oral Torah—in short, anyone who does not acknowledge the commandment of eruv…”
From Maimonides’ wording, at first glance it appears that someone who denies the Oral Torah and observes the Sabbath according to his understanding of the verses of the Torah is, by definition, not considered a Sabbath desecrator.
I saw in the Shulchan Arukh and its commentators (sec. 385) that they explained why the Sadducees are considered “not Sabbath desecrators”: because in practice they desecrate the Sabbath under compulsion, since “the custom of their ancestors is in their hands.” That is, this refers to people who are part of an institutionalized framework of denial of the Oral Torah.
But from Maimonides’ wording, it would seem that he is not referring to that. That is how it appears both from his general wording, and from the detail: “Sadducees, Boethusians, and all who deny the Oral Torah.” From “all who deny” and from the continuation, “anyone who does not acknowledge the commandment of eruv,” it would seem that this includes even someone who denies it as an individual, and not only as part of an institutionalized framework of denial of the Oral Torah.
Still, seemingly one could also explain Maimonides as speaking of “compulsion,” just not the compulsion of “the custom of their ancestors,” but rather intellectual compulsion—as the Radbaz wrote in his responsa, vol. 4, no. 187: “for his denial is only because he thinks that what emerged from his own analysis is true; if so, he is under compulsion and exempt.”
But Maimonides’ wording does not seem to indicate that he is speaking about compulsion, but about a real definition.
Honestly, this sounds to me a bit (or a lot) bizarre.
In your opinion, is there any truth to such an interpretation of Maimonides’ words?
And if in your opinion the answer is yes, do you think this halakhah has implications for other laws or other areas in Jewish law as well?
For example, if a Sadducee violates the prohibition of selecting on the Sabbath in the presence of witnesses and after prior warning, would he not be stoned?
In another area: someone who interprets “and they shall be totafot between your eyes” as referring to remembrance, like “upon the tablet of your heart,” etc.—would he not be considered, from a halakhic standpoint, as having neglected a positive commandment (and not merely as someone under compulsion because of his opinion, and the like)?
And so on and so forth, as God’s good hand enables each person.
If you have already addressed this halakhah in the past, I would be happy if you could refer me to it.
Wishing you a good and sweet new year