Issue with AoR or just me not understanding the system

[Jakoporeeno]

I'm currently playing as Athens. I've just taken the whole province of Hellas and have come across an issue or I might just understand the AoR system: I have Hoplite barracks in Athens and Holosideros barracks in Sparta where I should have more units to choose from than in Athens (for reference, here's the barracks in athens: https://imgur.com/a/vheYiyU and here's in sparta: https://imgur.com/a/LzkHiEv) and I noticed that on one or two occasions while trying to recruit more units I had more units to choose from that I guess is because of the AoR mechanic but they don't always appear every time I check the "recruit units" tab and I've noticed that when I have the recruit units-tab, if I press 3 (the button for recruiting units in my case) I see the extra units' unit card appear for the one tenth of a second where I press the button. Is this not supposed to be the case or am I just missing how this all works? Like, what is it that lets me see the extra units in the recruitment options and that doesn't let me see them? I'm confused. Here are some pictures of what it usually looks like for me: https://imgur.com/a/s2bR0Dk https://imgur.com/a/hUaEFyq https://imgur.com/a/jgY8Z7I but usually I don't see the units that are greyed out in the recruitment options.

[Dresden]

Those are reform units that will become unlocked after you reach various Reform tiers. Check out the reforms guide for more information.