yer it's as embarrassing for me as i bet everyone else here feels:
the UX of Microsoft is atrocious so don't feel to bad.
there is NO disabling the prompt, neither is there a "NEVER use NEVER set" pinkode thing.
however what you need to do is setup the pinkode, log of the system, at login there is a small text "signin options" in the bottom, click it and there is some small icons
(because the entire page needed to be covered by nothing, so no room for actual bottoms with text -_- mobile design for pc always annoyes me),
here you can choose the right one which is "login with microsoft account".
this does what you want.
you can now login with microsoft account without getting prompted for pinkode
(pinkode does exists now though and haven't tested if that will do annoying things in the long run. havent had to set it on my other pc's to avoid the prompt
PS: local login is not an option if you want the microsoft accounts to sync from the machines....
but guessing if nothing else have worked this was the last option used ^^