This ia sensei speciallity, almost always the seme is smaller and cute... while many times the uke is big, has a mean face and is stronger...
Also almost all ukes are older than the seme, in one case several years difference like in "Papa I love you" and "Baby I love you"...
There has been some complains about how sensei make alnost always the seme cute and smaller and the uke... but we can say the same about other magakas that the seme is always more manly and bigger than the uke...
For me I love how sensei makes the seme cute... it is refreshing when we see only bug manly semes in other mangas!!!
There is just something about a smaller seme dominating a bigger/stronger partner that's just such a huge turn on!! Like fuck, the duality!