I agree that it can be awkward sometimes but disagree on the specifics of when exactly it can happen. To me personally the gesture seems friendly but also slightly dominant and protective at the same time. For that reason it may be read as him accidentally establishing the power imabalance between him and the person he’s touching (with him being the more powerful one). In a youtuber-youtuber relation this power imbalance doesn’t really exist so my mind takes only about 0.001s to adjust to the situation and understand that the whole “power imabalance position” is only my gut feeling and not the reality. The reality being that it's just an expression of friendliness. However, in the viewer-youtuber situation, like in m&g, usually the power imbalance is indeed there so the position of his hands may serve to reinforce this fact to me and that’s when I sometimes, albeit very rarely, perceive some awkwardness.
I hope this was understandable (English isn’t my first language, yadda yadda). It made sense in my head. And honestly, I try to ignore these thoughts and focus on the cuteness and friendliness of the hand-on-shoulder situation instead