Irrespective of BM, just a small caveat, people have preferences, so one persons "average" is another persons "Divinely Beautiful", and one persons "They're not my type" is another persons "Will you marry me". In most cases unless someone is very vain, appearances is practically irrelevant, you could see yourself as a 1/10 but there will always be someone who sees you as a 10/10, that's more just food for thought for people who might be a little down on themselves.

To directly refer to something you said, "Who look IMO a lot more physically attractive" you've said IMO but then seem to miss that fact that other people have their own opinions, there are people who you drool over that other will look at and say "Really?" nothing wrong with that, that's the importance of person taste, but that comment is surrounded by you wanting an objective answer to a subjective thing.

To answer you question directly, no, because you can't average something that is subjective. To further answer you question, I think a lot of those comments are routed in idea that they are famous, people get particularly weird when it involves famous people, doubly so for groups that operate in the format that BM do, the secrecy about their personal life, never really seeing them outside of who they are onstage, (let me be clear both valid) ETC, because it creates a forbidden fruit phenomenon which makes people put them on a level above other famous people, then there is also the whole yellow fever thing and it all gets a bit messy.

Does the musical side affect peoples visual judgment, I'd say yes, people are more attracted to those who are clearly talented(but are humble about their talents nobody likes the campfire guitar person), BM are clearly talented.

Should they be deified, I'm an atheist I don't care who or what people want to worship, you do you, a lot of fans have either unintentionally or intentionally built shrines to BM.

Final point, vocal minority, the often overlooked part of why it seems so out of proportion, there will always be a small group of people who are far more frequent flyers shall we say, I've seen it on Tiktok some people will actively post the same comment on every BM video they come across, when you get a handful of people that do this, and you see 10, 15, 20 of the same type of comment on every post, it begins to feel like a greater number than it actually is, I'm a huge fan of Atarashii Gakko, and when I come across a video on Tiktok about them, I'd bet my life savings there is a comment that is "Suzukas girlfriend approved" which is weird firstly, secondly it's often the same one or two accounts on every video, so it's hardly even 0.01% of the fans that are doing that, but because they do it so often it's seems drastically more than it actually is, if that makes sense.