Lessons from the wise

Why not really determine that the rate is between 2-3 tefahim, and in the gray range discuss the laws of spikot. As we would do if kosher mikveh challah was a scientific fact whose full theory we have not yet discovered, but we do know how to reduce the range of uncertainty. Of course, if everything is convention, then we can save effort for the audience that obeys. Does challah occur according to the rate determination or was the rate determined in an attempt to capture the challah?

Last week it was announced that the Knesset had set an arbitrary number of 518 in some law, and Haim Katz explained with good taste that this number is a hundred times Hamsa and one more time Chaim, adding that we should not be surprised because this has been his custom from time immemorial to use such numbers in his decisions here and there and there and there is nothing to get excited about suddenly. [The truth is that sums of 5 and 18, very well dominate almost all possible numbers, so this is not really a limitation. Although if we reduce to ‘clean’ coefficients like 100,1 etc. then there are much fewer options]. He dismissed with disdain the speculation that there is some kind of interest behind this choice. In that case, it really seems clear that within the gray range we just want to determine a number and if a certain person likes hamsots and chaim, we will use hamsots and chaim, and may he be healthy.
https://www.globes.co.il/news/article.aspx?did=1001340473

Oh, actually, I just wrote after the first answer. Shiurin that, according to Chazal, were passed down from Moses from Sinai are a condition for halal (and this is even if the sages were given the authority to determine them, and were not actually passed down from Sinai), and if a person is not sure that there is a shiur, he should really act according to the laws of spikot and khazkot. And in the rabbis, there is no halal except within the gray area, they said shiur (and even there, those who are not sure should act according to the laws of spikot).

The Rabbi agrees with what is said? That the lessons are the same?!

”You are the one who is [Shabbat here.]

That is, the expertise of the sages was like those Canaanite experts, and not eloquence or prophecy.
In any case, why did they set a rate and not say, "Shak 38" or "Shak 40"?

By the way, Rashi [22:23] truly explained that they removed him from the court because he was a nuisance to them, but in the text -
”It is not to be interpreted because of the reasons of a word that is not common at all, that is, if one step is taken within fifty and one step is taken outside fifty, then it is a mistake to say that we should divide it by half, and it seems to our Rabbis that they should have restrained him because he did not measure at all more than fifty cubits, not even one step. According to all the measurements of the Sages, it is so. They found it between two shubchins. [And the third one is a shubhin, and the third one is a shubhin]…

And the wonder returns: where did the teachings of Chazal come from exactly like this?!

I didn't understand. The Gemara clearly says that the lessons are the LBM.
There are lessons that are quite clearly determined by the Sages. The lesson of Bagdad 3 Tefahim, etc. But it is still a lesson from Torah (except that the Scriptures gave them to the Sages).
This has nothing to do with prophecy or the LBM. According to the rabbis, this is their realistic assessment (like Bagdad 3 Tefahim). It has nothing to do with expertise at all. It is a matter of passing a line based on a consideration of reasonableness. That's all.
I don't see any surprise, nor why it is repeated. They set a certain lesson because that is how the halakhah works. It is unreasonable to set a lesson that is not clear. And yet to complicate things and ask about an unreasonable situation is to waver.