Ders: See what R’ Matisyahu Salomon says about this is Matnas Chayim on Purim.
And the fact that it’s in the Sha’ar Hatziyun and not the Mishnah B’rurah itself should say something. The M”B quoted almost every Shittah imaginable. The fact that a Shittah is quoted does not necessarily mean that he thinks you should follow it.