I have found extremely small changes are noticeable once I am very close to my target...Me too.
My first experience setting VTA was a Glider on the Graham 2.0 arm. Starting from the recommended near parallel eyeball method I listened and it sounded pretty good. Impressively good! Awful lot of guys would be happy and done right there.
Because it sounded so good I assumed it had to be awfully close and so I lowered it down only a teeny tiny little bit. Way less than 1mm. It sounded a whole lot better. So I did it again. Better. After doing this half a dozen times I got the feeling this could take forever at this rate so dropped it down near a full mm. Better. Again. Better! Dang!
Eventually, sure enough, lowering made it worse. When high the balance was thin and tipped up a bit. Lowering brought more fullness. Until suddenly it brought bloat. So back up. Split the difference.
Back and forth, up and down, splitting the difference, interpolating, until finally the sound kind of snaps in with supreme focus, clarity and balance. Those last few micro adjustments were so small, there's just no way anyone gets there without VTA on the fly. No way. VTA on the fly is no gimmick. Its essential.
Graham accomplished this with a side screw mechanism that came with the downside of being mechanically weak. So Graham added a set screw to lock in once VTA is set. Unfortunately locking the set screw changes VTA and is nowhere near as solid as if it wasn't there anyway. So much for the Graham.
The Origin Live Conqueror arm I have now uses a clever little mod bought from a fellow audiophile. It slides over the arm mounting tube and the arm rests on it allowing smooth VTA with no loss of mechanical stability. Only problem is it has no calibration marks, and causes the whole arm to rotate. So I had to mod his mod with my mod to finally have the perfect mod!
https://systems.audiogon.com/systems/8367The brass ring is his mod, the acrylic ring, measuring marks, and teak wood peg are my mods, and together VTA micro-adjustments can be smoothly done on the fly and reliably recreated in seconds.
Its amazing there are so many audiophiles that obsess over so much of turntable setup, in the most minute detail, spending incredible sums on all kinds of gadgets and gizmo's, then gloss over this one that is probably more valuable than all the others put together.