private key never leaves the device it is on; public key is .. well public so not something to store in a password manager. If the device is replaced, you create a new ssh key pair or restore your old one from a backup. In case your device is stolen/lost, you revoke access by removing the public key wherever you used it. This too is something a password manager can't do for you. If you are in a cloud environment, you let it manage keys for you. E.g. we don't provision any keys to GCP vms and instead login via a gcloud command that provisions temporary ssh credentials.
In short, I see no need for using a password manager for managing ssh keys. The public key is not something that needs protecting. The private key is something that you should not share between multiple devices or generally pass around.
But of course being able to paste your public key from some tool is nice if that is a regular thing in your life. And if you switch between multiple key pairs, it's probably nice to have something more user friendly than very fiddly command line tools. I guess the latter is what 1password is trying to solve here.
In short, I see no need for using a password manager for managing ssh keys. The public key is not something that needs protecting. The private key is something that you should not share between multiple devices or generally pass around.
But of course being able to paste your public key from some tool is nice if that is a regular thing in your life. And if you switch between multiple key pairs, it's probably nice to have something more user friendly than very fiddly command line tools. I guess the latter is what 1password is trying to solve here.