While I have no dog in this fight, I will say that unified mechanics (your symmetry here) does have inherent advantages that are much more compelling than the gratuitous "symmetry for the purpose of symmetry":
1 - It aids designers in creating intra-class balance (build/subclass balance) and balance across classes, across the level spectrum.
2 - It aids designers in better understanding (and communicating to the player-base) the component variables of group synergy and force multiplication across the level spectrum.
3 - It aids designers in designing and comparing monster

C power across the level and adventuring tier spectrum.
Together, those encounter inputs create a predictable model for encounter output which, in turn, allows for more focus on the other mechanical moving parts (such as battlefield dynamics and story/color elements) that create exciting challenges at the table.
Beyond that it also:
4 - Facilitates more rewarding, functional hacks and homebrew elements (from new classes, to monsters, to larger scale elements such as Encounter Cards or Mass Battle Rules) by groups/players/GMs...and therefore less wasted time on frustrating, dysfunctional hacking and homebrew game elements.
Tight, clear, math and symmetry is good for its results both in play and in the extra-play tinkering (same as any engineering project).