I don't care much for definitions - because dictionaries are often years or decades behind how words are literally used.

In this case it's a matter of breaking expectation - and not because the statement is "wrong". The statement would be correct but goes against what people are expecting when they ask such a question.

If someone were to tell you "My hobby is drawing." what do you first imagine? Perhaps not hyper realistic graphite drawings but you're probably imagining something with at least a mediocre level of talent. Decent proportions, an understanding of depth, at least the basics! How surprised would you be if they showed you a bunch of crudely drawn stick figures that look like a three year old drew them? Would you think they were pulling a joke on you?

If someone says "I'm a programmer" would it break your expectations to find out that they can only write `=SUM(A2:B2)` into an Excel spreadsheet? How many people do you think would disagree that they are "a programmer" if that is the extent of their programming talent? Do you think that would be a majority of people or a minority of people? If someone put on their resume that they had 8 years of programming experience and failed to mention that it was only with Excel functions would you count that against them when hiring them? Would you consider it manipulative or shady? It's the equivalent of saying "I handle financial transactions for a multi-billion dollar company." when you're a cashier at McDonalds. Factually correct, but you better only be saying it in jest or you would be considered a manipulative asshole.

By the way, my listed criteria did not exclude them. The first judgement is one of ability - all of them would pass as musicians by that alone.