>>44524163So I theorize that Pokemon do have varied sizes they are not all restricted to being one size. For example a Charizard is on average 5'7" but I could see one that's much taller like 6'3" or taller. If Pokemon Go/Let's Go is to be trusted sizes are wildly different.
Charizard for example in lets go can reach a max height of 7'10" and weigh 339.2lbs.