Problem with PIN Availability in Safe Mode

It's mostly likely because your account is online only mode (happens when you set up Windows 11 while connected to a network). I had an option to "create and sign into a local account" in one of these two areas (I think the one listed under accounts). It doesn't delete your data. You can sign back into your account later after safe mode, if you want. 

I personally do not like my account to be online only. I'll bet your option to remove your pin was also greyed out and couldn't be removed, which is how mine was when I was logged into my MS account. I ended up finding a way to delete my pin using a command prompt command and all that did was make it so that I could only then log in using my MS account, which took me to an online form and would fail same as the pin since no network in safe mode. 

Optionally you can just create another offline account with administrator access and log into that for safe mode and/ or just transfer all your stuff to it if you prefer an offline account.