Only with the $90 epic edition. Feels like a scummy move in a subscription based mmo. It's scummy at all times but even more so in this situation.
Taking into account that recent expansions have been heavily time-gated I doubt three days early access is going to give any significant advantage in the long run.
WoW has become a game about doing weekly chores and switching to an alt to do the same weekly chores.
But launch day was always a highlight. The energy was so good. This just breaks it up into the haves and have nots and that's fucked.
In terms of engagement sure. It's the ideal moment to do group content because everyone is still figuring it out and there is no lack of players willing to run.
I do agree early access shouldn't be a thing for an MMO. It might help alleviate some of the traditional launch day issues like queues and server load leading to issues, but they need to be able to fix those without pay-for-premium methods.