You are, of course, correct in what you've just said regarding the screws. Thanks for that clarification it is needed, but such is not really what I said if you read it very closely.

Sorry for the confusion, I was trying to avoid saying either type was too fine or too coarse for their applications, they're likely nearly perfect.

intended meaning:

The plastic screws are a bit finer pitch than normally seen in that type of screw.

The metal screws (self-tapping machine screws) have a bit coarser pitch than normally seen in that type of screw.

IOW, I'd expect to see at least a slightly more marked difference in pitch between the two types of screws. More coarse for the plastic ones and more fine for the metal ones.

I hope that's a little less confusing . . .

. . . somehow I doubt it. :/