I'm sure we differ on this also, and there's nothing wrong with that. In my opinion, learning consistent fundamentals (like grip pressure, stance, body positioning/alignment) allow for the development of a consistent golf swing or tennis swing or pool cue delivery.
There are different fundamentals involved with different types of swings, but each type has its fundamental foundation. The performance of the swing is the result of that fundamental foundation. And the quality of that result/performance hinges on two things: The quality of physical fundamentals and what's going on in your head, mentally.
When we make mistakes, it's typically not in our fundamental mechanics, not after we've ingrained them into our body and mind. Mistakes are generally mental. We get lazy, don't pay attention, rush shots, take shots for granted, etc...
If cue delivery were a fundamental element, then it seems we would always be able to deliver the cue perfectly, because the very definition of fundamental is root/core/foundation, the beginning blocks upon which we build everything else. And fundamental foundations aren't easily shaken or disturbed by mental laziness or distractions.
So, if the cue deliver is intermittent on given nights, it's likely due to the player's frame of mind and not some intermittent breakdown of a "fundamental" cue delivery.