Kind of. Sunders have their own unique loot table that is only accessible on tiers 4 and 5 heralds. This is unaffected by mf and by far the most likely way to get a sunder to drop.
However, on a T1-3 herald there is a tiny chance for a magic grand charm dropped by them to upgrade to a unique->sunder. This is affected by MF.
So yes, kind of.
Wouldn’t it just upgrade to gheeds?