Sam: This is one that, for whatever reason, in many cases stuck (or sticks today). Rav Sternbach in Teshuvos v’Hanhagos is matir in all sorts of ways (including, as someone mentioned, those that say the tzavoh was only for his offspring), but in this specific type of case (i.e. wife/mother), he still seems to be cautious about it. I’ve seen (or heard b’sheim – I can’t remember) the same from R’ Elyashiv zt”l and R’ Chaim Kanievsky (that one’s for you thabo) when I was looking into this inyon.
There are poskim that I’ve heard and seen matir (I’d name them, but I have no idea if it’s on a per-case basis or not – and therefore don’t want people saying ___ is matir).
Why this one of all the things he writes? Don’t know. I can’t say I’ve ever really understood these inyonim.