Is it trivially possible to determine the public key based on an SSH authentication attempt (without knowing the private key)? If not, then does it not make it

Is it trivially possible to determine the public key based on an SSH authentication attempt (without knowing the private key)? If not, then does it not make it less secure to broadcast it? While maybe this is "okay" for github to publish, they run a security-sensitive service and hidden API surprises like this could give some folks the impression that they don't take security seriously enough.