Normally I am using Modern Cards, too - the most Mac-like skin.
I changed it because of the crazy-tags-behaviour I mentioned in another thread.
Now I returned to Modern Cards but it's still the same: after restarting MC I
get the small window again (MacBook Pro 16" M1 Pro, MacOS 12.6, MediaCenter 29.0.87).
No suggestion why it's different on your Mac.
Frank