iMac loginscreen asks for pincode

I need sometimes a so called 'token' to sign documents digitally. Before signing a document it asks for my pincode and when it is right the document will be signed and so others can see the document was validated by me.

This 'token' is on an USB stick that I have to plug in my iMac running Big Sur (OSX 11.1). It can be checked by an app called 'tokenadmin'.

The problem is that when this token is plugged in and I let my iMac going to sleep mode I see my login-screen asking for a pin-code instead of my password. No matter what I fill in, pincode or password, neither is right. I have to remove the USB-token to let switch back the password field to 'password' and then I can login again.

Can anyone tell me if this is done on purpose? Or is this a bug that was already in the system before Big Sur and was not solved with the release of it. Is there a way to login without unplugging the token?

Thanks.