shulchanhashalem:
I’m not claiming that the Mishnah Berurah is the only sefer ever to use such a methodology. My point is that some poskim didn’t like that methodology, especially because it often changed the established halacha.
The fact that people wanted copies of the Mishnah Berurah does not indicate that it was accepted l’halacha. I own a lot of seforim which I don’t pasken in accordance with.
I quoted the sefer Minhagei Lita back on page 3, about how the Mishnah Berurah was not accepted. So I’ll quote two specific examples that he gives:
1) “The Magen Avraham takes issue with the Ari’s decision and concludes that even the Ari agrees to expose the actual fringes. Although the Mishnah Berurah with the Magen Avraham, he does not mention the prevailing custom does not follow the Magen Avraham. No one in Lithuania wore his tzitzis hanging out as people do today, not even the Rabbonim, not even in Radin” [emphasis added]
2) “Despite the suggestion of the Mishnah Berurah to repeat the word zeicher to acomodate the opinion that the reading is zecher, in the Telshe Yeshiva and most other places in Lithuania they did not repeat it. In fact, according to former talmidim, they did not observe this custom even in Radin, where the Chafetz Chaim had his Yeshivah.” [emphasis added]
If you have any counter-evidence regarding these two examples or about other cases, I would be interested in hearing it.
Also, I’m not claiming that the Gra’s popularity is entirely due to the Mishnah Berurah. All I’m saying is that it definitely contributed. My point was that like the Mishnah Berurah, in his time the Gra was not generally followed.