I’m not sure about this change. It feels like it’s not a change made for balance, but just because the UI can’t handle more keys, which also was a problem with the Dutch at one time. I posted the bug that the Nizam lost volley and stagger mode because their ability took that space (Nizam Fusiliers bug with Battlefield Construction - Age of Empires III: DE / III - Report a Bug - Age of Empires Forum), and also proposed that if it was possible, use a dynamic UI that could hold more columns ( Proposal: Dynamic UI for units and buildings? - Age of Empires III: DE / III - Discussion - Age of Empires Forum).
(Something Like this)
I’d even prefer if formations took 2 rows, having one bellow, because you never really lost them, you still can use the formations with the hotkeys. This issue is also present with explorers when you revolt or gain more abilities, and it wouldn’t be a good fix to just remove some abilities from them.