i thought the same about a gm the other day. i think they're all the same size gm's, one fitted on near the tightest snaps, the other i could barely do up. bizarre!
t has a toddler bug hun, he's 8 months old, as well as mediums and m/l the toddler bug just needs no extras and rarely a wrap either!
I've given up with size 2 tots bots and only buy size 3s now. And if I was going for a bed bug (which I can't as we can only do full minkee lined stuff )I'd def go toddler sized.
I think part of it is that as they grow bigger they thin out - though Miss C is 98th percentile so she's always going to be odd