It simply isn't sounding good Cameron. The quote from the rulebook does indeed answer your original question. If you're looking to clarify the wording for future rulebooks, that's fine. But if you're trying to score a bank by challenging the wording of the rules, then that is on the edge of cheating. That's my opinion.
I think you know better, and hope that you're simply looking for a different rule wording. The answer is no, you cannot simply shoot a ball at the pocket, and purposefully kiss the adjacent rail going in, and call it a bank. Isn't that the simple answer? If you try it in a serious bank game, don't expect to get away with it.
The bank rules say "no straight-in shots." Yes, another ambiguous rule, but the intent is clear and addresses your shot.
Steve Booths proposed bank shot rules also covers your shot:
"7.5 When a called ball contacts either the cushions or pocket points along the rails adjacent to the called pocket on its final approach toward the pocket, such contact does not count as a bank in defining the called shot. If an otherwise legal called bank shot is pocketed in such a manner, the ball counts as long as the shot conforms with the shooter’s called intentions, and no foul or scratch occurs."
That gets rid of the word "incidental," which I'm sure is the word that has you confused in my previous quotation.
Fred