Is the infidel in the Toshevaf and keeping Shabbat according to his understanding defined as a desecrator of Shabbat?

Good evening Rabbi Michi,
Happy holidays
I recently came across what Maimonides wrote in Halachos Eruvin, Chapter 2, Halachah 16:
"An Israelite who publicly desecrates the Sabbath or who worships the stars and the omens is like worshipping the stars and the omens in all his words… But if he were one of the Epicureans who do not worship the stars and the omens and do not desecrate the Sabbath, such as the Sadducees and Bethuselites and all the infidels in the Oral Torah, in short, anyone who does not acknowledge the commandments of Iruv…"
From the language of the Rambam, it seems at first glance that the unbeliever in the Toshabeh and who 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 Arba and its commentators (see Shabbat) that they interpreted the Sadducees' thinking as "not desecrating the Sabbath" because they are actually desecrating the Sabbath by rape, since "the custom of their fathers is in their hands." This refers to people who are part of an institutionalized system of heresy in Toshvaph.
But from the language of the Rambam it seems that he does not intend this, this is evident from his language in general, as well as from the detail of "Sadducees, Bethuselites, and all the heretics in the Toshvaph." By "all the heretics" and from the continuation "everyone who does not acknowledge the mitzvot of Iruv" it seems that this also refers to someone who is a heretic as a person and not as an individual in an institutionalized system of heresy in the Toshvaph.
However, seemingly, even in the Rambam it can be explained that this is a "rape", but not a rape of the "custom of their ancestors" but a rape of the mind, (as in the words of the Radbaz in the Radbaz Responsa 4:17, "…whose apostasy is not possible except because he thinks that what has arisen in his mind is true, and if so, he is raped and exempt")
But in Maimonides' language, it does not seem to mean that he is talking about rape, but rather about a true definition.
Honestly, it sounds a little (or a lot) "disturbed" to me.
In your opinion, is there truth in such an interpretation of Maimonides' words?
And to the extent that you believe the answer is positive, do you think this halakha has implications for other halakha or areas of halakha?
For example, will a Sadducee who violates a "arbitrator" in the presence of witnesses and a warning not be stoned?
In another area: Would one who interprets "and they shall be as drops between your eyes" to mean a matter of memory, such as "on the tablet of your heart," etc., not be considered halachically as nullifying a positive commandment (and not just as a violation of his will, etc.)?
Etc. etc. As the hand of God is good upon everyone.
If you have already addressed this issue before, I would be happy for you to contact me.
Wishing you a happy and sweet New Year