Honestly, I don't get the point of it. SSH keys, unlike PGP keys, are meant to be disposable and don't carry any identity information. If anything, I'd rather use my PGP keys with SSH (an option available for about a decade I think).
But they use SSH keys to push to GitHub anyway, so someone added the option to use SSH keys to sign Git commits. Now everyone can have a green "Verified" symbol on their commits.
It's worth less, but it looks better!
Does it have a checkmark? Yes? Must be secure then.