>You’re making a wrong assumption. Not every Mechallel Shabbos has the status of an Apikorus.
I didn’t say that.
The closest I probably got was:
from https://www.theyeshivaworld.com/coffeeroom/topic/who-is-a-jew#post-2502092
3. There is a red line of who is part of “amecha” (am yisroel/klal yisroel), and those basic requirements are 1) keeping most common mitzvos, 2) believing without doubt the 13 ikarim, 3) keeping shabbos publicly. Like any sugya, there is much beautiful Torah iyun in each part of that “red line” (what means “public”?, what are the exact terms of the ikarim?, etc) , but the red line exists whether we can identify the minutia of its precise location or not.”