Didn't work for me... ☹️
EDIT: actually the procedure did work, I just had to restart the watch.
I'm on beta and couldn't get assistant working on the watch 5. Small box opened on the phone. I installed the most recent assistant apk from apk mirror. June 1 and was able to get assistant working on the watch after that
Just got an update on the watch and got Assistant working.
Of course. This is my first watch, so I'm not sure which you need, but here is a screenshot of my current software versions. All I did was check for any available updates.