there is a very strong correlation between your elo and your knowledge of the game, but it's not a necessity, especially if you were a good player of a similar game. There are things you only learn from experience, it's inevitable. I would never say that a commentator who doesn't have a background in a similar game and has never reached a high level knows more than a professional player and, similarly, I would tend not to say that someone with that profile knows more than a high level player. Although there is the possibility that the commentator understands more than the professional player or the high level player, it is very unlikely. It's not a necessity that you need to be a high elo to understand the game, but denying that there is such a strong correlation is crazy.
I don't think a caster necessarily needs to be high elo or have been high elo in a very similar game, but I think it's preferable that they hire commentators like that if they're the analyst type. For me, a commentator needs to bring something extra and it doesn't necessarily have to be a technical look, I wouldn't have problems if the commentator was a charismatic and/or funny figure too, for example
at the end of the day i slightly disagree with Subroza, the topic was more about the Brazilian commentator Melão