The cap favors tall empires
Do they need it though? If Tall is expanding until you establish borders with your neighbour then investing in your economy to grow, while Wide is investing in military and invading your neighbours to grow, and these are brought to a balance somehow(Pop growth sources), then each group should be receiving relatively equal benefits from their respective number of Leaders.
A Tall empire is going to have high level Planetary Governors, high Level Assist Research Scientists, and the same number of Council Leaders acting on worlds with Planetary Rings, Ascension levels(which on your Capital and Habitats includes Research Output %), Ring Worlds, Ecumonopoleis, Habitats, and Megastructures, all with minimal Unity upkeep on top of less sprawl effect on their Unity and Research value.
A Wide empire is going to have very few of these bonuses, a similar number of core worlds which should be less developed, and a bunch of tiny resource and Pop growth worlds which receive minimal benefits from Planetary Governors. This is on top of much higher Empire Size maluses which makes spending your Unity on Leaders for every size 12 mineral world a big waste as they cost more and return less.
All else being equal, both these empires are going to need the same number of Leaders on the Council, the same number of Science Ships(which is dependent on Galaxy settings unless you are deliberately stopping your explorations to turtle before borders force you to), the same number of Fleets(if they have more Fleets than you of equal or greater size it doesn't matter if they have Admirals), and more Generals would just make the mop up a tiny bit faster.
The only real difference is between the number of Governor and Assist Research slots one will have available, and since we are discussing hypothetically equal empires they have an equal tech income to boost. Since they kept the ability to freely move Leaders around, most of the old Leader traits were redundant and you would only gain
percentage bonuses to tier 3 resources(or Food lol) which are best developed on a specialized world. The problem arises since they added all these stat stick Traits to both Governors and Assist Research while making Governors Planet based, which they then capped which ironically made most of these bonuses useless by bloating their Unity costs and forcing us to choose only our best Leaders to keep around if we want more Traits.
Tall vs Wide balance is off due to how quickly one can acquire Pops by letting AI empires grow them for you, unless there is a new Pop Growth trait for non-Council Leaders then this cap only serves to limit these shallow free resource traits and I'd rather see them both go.
