In my view, whether spark plugs or TEV's, their adjustment is just simply the last thing to look at. The last thing to touch. Having your timing correct is primary, for example with an automobile engine. Knowing temperatures and pressures and such is primary with a refrigeration system.
I like this analogy. There are factors which have a much greater effect on system operation than precise (as opposed to ballpark) TXV superheat setting, and most techs have no idea what precise superheat setting means anyway.

It's been a long time since I was an auto mechanic, but if I had a choice between precise adjustment of the timing with ballpark spark plug gap, or ballpark timing with precise gap, I would take the precise timing every time.