I have to agree this is so annoying- just cannot make a Watch face that I like with the complications I want.
I found the following Apple page with what Watch faces have which complications.
https://support.apple.com/en-gb/guide/watch/faces-and-features-apd6ce85daf4/watchos
As you can see this does not appear to be a bug but something that has designed in such away.
Rubbish in my opinion.
Ickle
I totally agree...I don‘t understand that...