It’s really not - by limiting the life of keys, and having a service generating them, you can more effectively lock things down when someone leaves, rather than going round revoking keys from servers. Something we’re experimenting with at work is AWS Instance Connect, which uses your AWS credentials to push a key to a target instance with 1 minute validity - no more managing keys on instances, and revoking access is just a change to an IAM policy.
As opposed to having a few bastion-hosts, and requiring people to log in there in order to then ssh on to their final destinations -- in that case, revoking their keys is as simple as wiping their accounts on the bastion hosts.
Even with a few bastion hosts things get hard to track quickly as you end up with multiple clusters (dev/staging/UAT/production), and potentially multiple production clusters in different regions.
It seems weird but has several advantages. Most places screw up defunct account cleanup and privilege management.
A process like this allows you to ensure that people have the access they need and makes it easy to get them the privilege separation needed.
This is weird. Really weird.
Did that service use a more secure authentication storage than a password protected key?