Just wanted to add to the 40 pages of replies and over 5600 people who have indicated that this is also a problem for them. Microsoft, PLEASE give us a way to disable this.
My situation: a Windows 10 NUC that I bring back and forth regularly between two locations -- and have for the past four years. This problem started just a couple of months ago. It is unclear whether rebooting roughly 10 times per week is what now causes the issue or whether the occasional mistyped PIN did. There is ZERO feedback about what metric is used for determining either of the conditions, which one was triggered, or whether there is a way to configure the detection. Interestingly, I see here that some people have been having this problem since at least two years ago, implying it didn't arise from a recent update. It is mystifying how it started becoming a problem for me only recently.
There also seems to be no effective reset to get back to the PIN-only login I was able to enjoy for the past four years. I can get it with my Microsoft online account password, but that's a 20 character string of random characters that I can't even effectively enter with my password manager, because of course the password manager is not available until after login. Once I log in successfully, it isn't long before I encounter the situation again -- probably on the next login. That's what just happened now, leading me to this thread. I was forced to login with my password about 18 hours ago. The computer stayed up all night, then I shut it down, brought it to my office this morning and AGAIN had to do password login because PIN was disabled.
I am not saying the feature necessarily needs to go away, but it really needs to at least have better documentation and give us more control over it. And Microsoft really ought to comment on the situation here rather than having 40 pages of people all hunting around for more information about what's going on.