There are a lot of inconsistencies in those lower divs that I have no clue about, and I agree it should be consistent.
This being said though, I don't agree on someone being invite on a class and then playing that class in div 1. If you are div 1 on a class you shouldnt be allowed to play div 2 and that should be consistant.
To my knowledge ether, exile, donovin, and um all planned to play invite this season and held their own on invite teams against other invite teams. Ether and exile were on their own team, Donovin was either gonna be playing for mustard or 8k, and um was on the perfection team even post perfection not getting unbanned.
I'm pretty sure the mirror man class restriction to pyro was a meme because that team was centered around the fact that mirrorman said he would never play a season again unless he got to play full-time pyro. That being said i feel like his class ban should only come if hes invite capable on demo and scout which im not too sure about.
Monsta, im pretty sure, has played both scout and Demoman in invite and played soldier at times for his team which has consistently made top 4 for seasons. I have no doubt he's invite capable on that role.
I want to make note that the most inexperienced invite team this season is virgils team. they are made up of basically 2 teams from last season. 1/2 of virgils team who placed 6th, and 1/3rd of sinkarma's team who placed 2nd. despite this they do well in invite against other established teams in their scrims. I see no reason why anyone whos made top 4 on a class isn't invite ready. On top of that with more low invite teams there's more competition meaning more close games, better scrims, less of a chance going 0-16.
This is just a personal opinion but I'm pretty sure the people with high leniency on their class are also the people that decided they would play low invite last season. the people with harder class restrictions are the ones who have been making div 1 top 4 for seasons on end. Ether Exile and Alexandros all are playing classes they are invite capable on in div 1 but they were also willing to play invite last season.