“yubioath” does not decrypt smime messages

[tigernero79]

At this link:

https://www.yubico.com/blog/uncovered-piv-use-cases-on-ios-using-yubikey-as-a-smart-card-on-ios/

yubico talks about the possibility of extracting public certificates and inserting them into the iOS keychain. public key smime which would be used for email apps for what? Signing a message works by making the yubico Authenticator interact with the yubico 5 token via NFC. and so far ok. but if you try to decrypt a smime certificate received from someone else's email. the private key that worked to sign my email by interacting with yubico 5 via NFC was not zipped to decrypt emails received, including replies.

so I wonder what utility there is in using yubico Authenticator since it does not allow me to decrypt my smime emails received. What is the point of placing a public certificate via yubico Authenticator? to make it interact by signing my email and sending the public certificate attached? Could you kindly explain the meaning to me?