This decision may be in part why they'll allow infinite (?) complete resets. It will have to be viewed in the framework of this mechanic existing.
I'm personally much, much more concerned about the power boost... combined with the lack of requirements. If I got this right, Larian will make fireball available to every level 5 character, multi class or no. Depending on just how unhinged this implementation is, the lack of requirements can be varying levels of disastrous. Go 5 levels paladin, one level whatever for fireball...
We may be all able to agree this is crazy and "just don't use fireball?" facetious. The issue is when it becomes tolerable enough for some people to ask said question again.
It sounds more like they are implementing the multi-class spell slot progression, but then letting you cast spells with those slots from any of the classes you chose. So you would only have access to the full spell list of everything if you took at least one level in Cleric, Druid, Bard, Ranger, Paladin, Wizard, Wild Magic Sorcerer, and Warlock.
Those rules would also dictate that you would need to be one level of an arcane class and 8 levels of Paladin to get fireball. 1+8/2 for the spell level progression.
