I don't even know what will qualify an individual as a professional and if it is being knowledgeable in different gambles, they I should have been awarded a professional. I don't believe in that idea of a professional gambler because the moment you gamble consistently and is able to manage gambling addiction, there are high chances that your knowledge in gambling will increase and you start to make informed gambling decision. Maybe at this point you can be called a professional gambler.
Who verifies there is a professional gambler, how is the standard? This is a big question in my head as a gambler, is he who has a long experience in gambling or what?
If you look at professional standardization then he has serious expertise in that field, of course his victory should be much greater than the defeat and history is much more victory.
Maybe it's someone with a lot of knowledge and experience in gambling enough to call themselves a professional gambler. Just like any other profession, they have their own category to call them a prof. The difference I think, is that while most jobs involve risking time, energy, or even safety to earn money, a gambler risks their own money directly to try and make more money.
If we're talking about the definition of a professional, it should be understood as someone who is capable. Therefore, if someone doesn't have a proven track record of winning in gambling, they can't be called a professional gambler. That's the standard, given the general perception of the word professional.
If it's only about insight and experience without betting skills, I don't think it's appropriate to call a gambler a professional. To be considered a professional, a proven track record is essential.