This isn't pointed at any one person,just some stuff I've noticed over the years while learning to draw muscular people (men especially since I don't draw women that often). I've seen lots of folks draw the abdomen muscles incorrectly (not that I'm any kind of expert I simplify a lot).

However I have picked up a correlation about body types and what a person is mostly likely to be doing vs the ab muscles.
A fast swimming, active person for example would typically have a flatter stomach, with six, maybe eight pack abs (The human body only has 8 abdominal muscles so stuff like 10 and 12 packs are virtually impossible). Bodybuilders who only lift weights and do gym exercises are only going to have a defined 4-pack usually with the third set visible but not very well defined. This is due to the fact that running and swimming are what work the lower abs so its not as likely for a straight up bodybuilder to have a 6 or 8 pack.

More muscular flying humanoids are most likely to have toned but not super expressed abs but are very well built in the chest and legs.
Nagas and Merfolk are likely to have six or eight pack abs due to the way they move.

This is just a generalization and I am in no way saying that you can't have other boy types this is just more focused on muscles and how activity and what the creature does would relate!