You've hit the nail on the head; some people (certainly myself) find it hard to describe a character's precise features and so describe them in terms of their presence instead, which lends more to ambiguous descriptors like 'tall' and 'chubby' than it does to facts and figures; that tends to be the default way of describing things in fictitious prose, as far as I've noticed. It's not that I don't think those details are important, but I assume, if relevant, that stuff will naturally unfold in the IC anyway.

The fact I straight-up don't know how tall a human person is or how much a human person weighs is probably related.