Is the essence of the problem still not clear, and are the alarm bells about the possibility of changing this not being heard? "Picking on" the tag is NECESSARY! After all, search engines latch onto it. A tournament must simply live up to its name. To define it by all possible and available means! Create a topic and put forward a proposal on how to differentiate between newcomers and non-newcomers. The organizer should not only hand down verdicts but also communicate with absolutely everyone, like you, for example, were/are interested in all the nuances about the state of gamers' ability to play in your tournament. This is work, not just a title. Communication skills are the most important component.
It's much easier to automate recruitment than to select players to your liking.
A newcomer is someone who has recently started playing Heroes, not a pro from another portal who recently registered on HeroesWorld! Strong players are usually known by all, while unknown nicknames require separate eligibility processing. The difference between a noob and a newcomer is huge! A noob is essentially a hindrance to development, while a newcomer can develop quickly if they know their stuff well.

Now you ask, how to tell them apart?

And how can you call a player who has been on HeroesWorld for a couple of years a newcomer? Beyond comprehension, simply absurd, what more is there to say?...