Question

I accidentally deleted the question. I’m reconstructing it here:
I grew up in Bnei Brak and studied in the Talmud Torah at the Chazon Ish’s school [Tashbar]. When it was the Sabbatical year, some of the students treated leftover fruits and vegetables as having the sanctity of the seventh year, even though they came from non-Jewish produce. Some did not. When I looked into it, I was taught that the sanctity of the seventh year does not apply to non-Jewish produce, except for followers of the Chazon Ish who do treat it that way [a few percent of the population], and a few baalei teshuva as well [whose tendency to be stringent is understandable…]. That was also the practice in my parents’ home and among the neighbors—they did not follow this stringency.
Now I saw a book by a respected knitted-kippah rabbi who writes that although there is no need to treat non-Jewish produce as having the sanctity of the seventh year, in Bnei Brak—where the custom of the Chazon Ish was accepted—one should indeed treat such produce as having the sanctity of the seventh year. Therefore, in Bnei Brak, that is how one should act. But that rabbi is mistaken about the facts: Sephardim, Yemenites, and Hasidim obviously do not follow this in Bnei Brak [and they are the majority]. Among Lithuanians, too, in practice only a minority actually follows this. So is the Jewish law therefore different from what that rabbi wrote? [He is mistaken about the facts]