Nope, you were right. It's for USB MITM. I guess the assumption is that the keyboard is wired in a different way (a laptop?) or in wireless scenarios (NFC Yubikey).
Re:Show HN: GPG on macOS and YubiKey
by trishankdatadog on Wednesday November 13, 2019 @07:23AM
(#21523266)
Quality discussion, both of you, thanks!
Interested to hear what it's for