Explain to me again how this is better than just a password ?
Because a 4 - 6 digit PIN you can remember, while a 20+ character password you write down and in many cases store insecurely. Some even store it on a post-it note next to the keyboard.
As for remembering 20+ character passwords, "Correct Horse Battery Staple" (https://xkcd.com/936/) is a fine method for passwords. It doesn't have to be serial port line noise.
However in this case, the Windows 10 "PIN" can actually be a longer password.
So why is it better to have a longer PIN instead of a longer password ?
If a PIN is just another password with the same length/complexity requirements as a regular password, why should i bother ?
Seriously, though, PIN implies a number for a reason (even if people don't think about it or say things like "PIN number"). They should expect confusion if they refer to a password as a PIN.
How on earth would a 4-6 digit PIN be more secure than my 20+ character password ? In the end, an PIN is just another password. They may employ a million iterations to their KDF, but 6 digits is still a lot easier to bruteforce than 20 characters.
As for the rest, fingerprint and face, they're not secure. Convenient yes, secure no.