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.
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.
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.
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 ?