I think the point you might be missing from the OP, is that the person in question doesn't actually possess this knowledge or skill, but instead of being humble and admitting the gaps in their knowledge, perhaps asking a question or two when they don't understand, they just plow ahead.

I know people like this. It's not malicious I don't think, maybe it's more of a defense mechanism? They don't want to look uninformed, so they try to fill the gaps in their knowledge with assumptions. Maybe they're right a decent amount of the time, or close enough to fool people who aren't knowledgeable on the subject. But people who are knowledgeable, will recognize what they're doing, and the lack of humility comes across as arrogance, even though that may not strictly be the case.

It's normal to know a lot of stuff and like a wide variety of things. But you need to be humble when you don't know something.

When I don't know something for sure, I like to say "I think it's this way, but I could be wrong." Or something like that. Or heck, if someone else has the knowledge and skills I don't, I'm right up there asking questions, I want to learn. Maybe I'll try to impress them with what little I do know on the subject by commenting or asking questions in a way that shows I understand what they're talking about, because we all want to have self worth. But faking it isn't cool, and can be harmful, or just annoying.