Yeah, I also feel that just unlocking everything is more in line with Larian's design philosophy. They really don't want multiclassing to have negatives, just like they don't want you to feel locked in to anything--like how Barbarian can just change what Heart they're using, respecs are available, etc. Ultimately it's going to be fine because of the action economy, spell slots, and concentration, so I'm not too worried even if we end up with much larger spell lists than would make sense by RAW.