318 Heads: bad valve job?

What you see on the tip height variation is common on rebuilder valve jobs, I have to fix that on most heads that come in. They should all be the same height within .005"-.010" , performance stuff less than that.
Maybe not a deal breaker as stated but not what I like to see.
Grinding stems down to match is another hand slapper/no-no. Cut the seats to the same depth like they should be.
Spring pocket depths vary in height, so that is not a safe datum to compare one to another, that's why some seats take more shims to get the correct installed height for the springs.
I don't know any professional head guy that will use a Serdi (or Rottler) to cut seats, especially the big stuff, most of the guys I know use a vertical mill instead as its much more rigid and produces results easier.