Tested on a Windows 10 VM running 21H1 - 19044.1288. Gpg4win version 4.0.0, GnuPG 2.3.4.
When using a smartcard with the latest version of Kleopatra for the first time, any operations fail with message "unusable secret key". If the smartcard is then used for the same operation via command line, the operation succeeds, and a shadowed private key file is created under %appdata%\gnupg\private-keys-v1.d. After that key file is created, future operations using the corresponding private key succeed in Kleopatra. If that key file is ever removed, Kleopatra fails again, but the command line continues to function and automatically generate the key file.