Trolls, like Jotun, can be both monstrous or humanlike. In Scandinavian folklore a troll is more of a broad category than a specific 'species'. The main thing is that they are malevolent and supernatural. Some trolls are grotesque creatures with a dozen heads, while others are so human like that they can exchange their children for human children without the human parents ever realizing. Following is from a Danish historic dictionary:
«1) according to folk belief: a supernatural being hostile to humans (dangerous) (of a more or less human-like form), especially of supernatural size and strength, ugly (creepy) appearance, thought to live in hills (mountains), forests, etc. (cf. Hill, Mountain, Sea, Forest troll and underground); also of smaller beings such as dwarfs or gnomes (Junge.308. NPWiwel.NS.22. Feilb. cf. Small troll)»
I mean orcs are wretched elfs so it makes sense to draw them very human in some sense.
I think my view was very much inspired by DnD. It is interesting to note how different this stuff were viewed at the time.