The answer is very simple gatekeeping and toxicity.
I already see a lot of players in the game already rejecting players simply because of their low roster level and this will happen even more in the future.
Let’s say Scouter gets released 5~6 months later it’s very hyped class after Lance Master and so many people wanted to play Scouter, so they just started playing the game with Scouter release and you’ll also have returning players, but as soon as they start doing end game content they will be constantly rejected.
They will be rejected at least 70~90% of the time simply because they aren’t above 100 roster level yet, so people will easily assume that this person hasn’t done most of their horizontal content for skill points and probably lack experience in the game and most players don’t want to deal with that.
Some of these Scouter players will just end up quitting the game anyways after realizing its just not worth it to deal with all the toxicity and gatekeeping or AGS will have to nerf legion raids and Argos, so most of the gatekeeping is unnecessary.
However if the players got to play the class they wanted, they are more likely to work towards their character and get to experience legion raids which is the games best selling point before they face most of the games toxicity and gatekeeping.
Classes being “content” is simply wrong, not everyone is interested on playing Destroyer and waste a character slot on that class, so May update in terms of “classes” doesn’t really seem to be exciting for many players except a few, they will be mainly excited for the Valtan release.