If this was a custom option, you wanna engage in the circus mode. Click the checkbox be happy with it.
But making it core even for Tactician? Makes zero sense and just makes the game designer looks lazy, I understand that 5e has serious issues regarding character identity and customization, but this is due to some factors.

Feat selection and progression.
Class choices and interactions
Weapon interaction and maneuvers (Larian fixed this thankfully by adding maneuvers)

The optimal way would had been homebrew new feats for BG3 and add 3.5 feat progression.

1st
3rd
6th
9th
12th

Basically you would have more interesting ways to define your character build without resorting to lets make pure classes useless. Because with this Multiclass no restriction you need to be a sucker to go pure class.