I don't know much that invalidates also having a natural tendency to read one side or route combo option first.
I mean, yes, you're right, most plays have a designed route concept, and that should be your first read. Not arguing that.
But most plays that aren't run out of a trips or bunch formation actually have more than 1 (3 receiver concepts like Floods are a good example of the exception)...either mirrored or 2 different concepts.
Curl Flats out of a Dice set...you have mirrored Curl Flats on each side, TE/WR on the strong side, SLWR/WR on the other. Which route combo do you naturally watch first?
There are textbook answers for that, too...which one is to the field side (giving the flat route more room to maneuver after the catch), and which one has the better matchup?
But even knowing that, we still have tendencies. Like I said above, my habit is to track to the TE first. So even after a pre-snap read and an informed decision, I bet you anything I'm going to read the strong side concept first unless I consciously remember not to.