It doesn't, yeah. And people I've played with have already been confused by grappling existing as a skill check, let alone if it interacted with other systems and the GM judgement calls on someone's bodyweight + equipment weight.Related question to this - how often does this come up?
You are right! My reading comprehension failed.Aa, the official name isn't variant encumbrance, implying the default is encumbrance, but it's variant: encumbrance. Oops.
It literally states the limit is twice your carrying capacity, though? Your speed is 5ft if it goes over once your carrying capacity.
I'm not sure what you mean by "deviate". The rules for moving a grappled creature state your speed is halved unless the creature is at least two sizes smaller than you, and the push, drag, or lift rules state your speed drops to five feet while pushing or dragging something over your carrying capacity, so it stands to reason that, when dragging a grappled creature that's not two sizes smaller than you, your speed is two and a half feet. This seems coherent to me.But as fluffybunbunkittens has already mentioned, the movement rules with respect to moving around the creature you're grappling already deviate from the rules for dragging and carrying.
And none of this seems to follow,So any inference that you should interpret drag and carry as using the same rules on page 176 is weakened. Better to just not worry about it since there's already a rule in place to keep a player from grappling (and thus moving) anything 2 sizes larger than themselves.
As a general matter I would say carrying capacity does not come into play. That said I as a DM I would disallow anything patently absurd. I don't care what the rules say, an elf can't put a stone golem in a headlock and drag it around.