If all that is required is human readable version info, that is still obtainable from apk for openssh-client using:
~ # apk info openssh-client
openssh-client-default-9.3_p1-r3 description:
OpenBSD's SSH client
openssh-client-default-9.3_p1-r3 webpage:
https://www.openssh.com/portable.html
...
As to apk version, firstly apk version any_unrecognised_string returns exactly the same empty output. I think this is because openssh-client is a meta package, a collection of other packages bundled for convenience. Like build-base, but unlike build-base perhaps all openssh-client's metadata hasn't yet been provided by the uploader.
apk add openssh-client installs 3 applications (and perhaps more). This can be seen by doing:
~ # apk info | grep openssh*
openssh-client-common
openssh-client-default
openssh-keygen
Version info for each of those programs can be looked up using its full name, e.g. apk version openssh-client-common. Or for all three by:
~ # apk info | grep openssh* | xargs apk version
Installed: Available:
openssh-client-common-9.3_p1-r3 = 9.3_p1-r3
openssh-client-default-9.3_p1-r3 = 9.3_p1-r3
openssh-keygen-9.3_p1-r3 = 9.3_p1-r3