kasha,
Except for the times we don’t hold like the Rema. (See hilchos shaboos discussions as related to cutting up vegetables as it relates to tochen, mi’yad and borrer. M.B. 321 s.k. 45. In this case we are more machmir, but there are times the MB is more meikel such as salting food on Shabbos which the Rema says is assur but MB says HAMACHMIR tavo alav bracha.