The branching timelines of the Sacred Timeline are stated to be bigger than it, I know that infinities within infinities is still 2-A, but what I mean is that each timeline of the multiverse is a 2-A structure since they are bigger than the Sacred Timeline, which already contained infinite universes and realities
The multiverse at all points was 2-A and was never enlarge after Loki, it's just that Kang wouldn't destroy anymore Kang timelines.