Yes, but he is also under a lot of stress and he doesn't eat as much as he should. While stressed he's brain realising cortisol (and probably other hormones), which really mess up your body, not enough kcal and protein makes it even harder for him to build up, because he's burning more than he receive. I hope it's help
Remember to find some activities that reduce your stress, fx coloring book, crocheting, knitting, drawing (repetitive stuff) it help with stress and also stop your brain from deteriorating and "stops" you from getting early dementia or Alzheimer!!
Agree w/randomnick but also sometimes its just genes. My brother and husband both work labour intensive jobs (oil fields and pipe work) + work out and at most theyre lean. They weigh no more than 150lb neither taller than 5'9. If they wanted to bulk itd be expensive bc theyre need to eat a lot and they would need to near their weight in protien and also eat more calories than they expend. For me its easy for me to bulk, but difficult for me to get lean like them bc while it is easy for me to build muscle its just as easy for me to carry fat.
Average person expendes 1700-2000 thats moderate activity (i.e. Working out 2-3x a week). Labor workers can expend 2500-3000 depending. So theyd have to eat 3000-3500 calorie wise and to build muscle 150g of protien daily. Thats estimate is mega rough bc genes play a role and so does sex. Anyway, one of the most impottant part of building muscle is Rest. Rest time is important bc its the time your body literally builds the muscle. Specifically, after your muscle fibers tear dueing workouts the rest time is when its repaired and strengthened.
So he eats poorly, gets little sleep and expends tons of calories so his stature makes sense, kinda like a biker but since he obs doesnt work out, he mostly has labor muscle which isnt as flashy as muscles gained through work outs.
That was a whole lotta info dump so if you made it this far i hope it was informative lol
Considering that Yeomin handles light or heavy workload for years, shouldn't he be a little buff? lmao.