Hmmm, good question. I think it could be argued that the conical taper 'may' hinder the players ability to shoot straight simply due to the constant changing of diameter through his bridge while stroking.
Another difference could be flex point, which is seldom talked about or acknowledged. The conical taper will flex most in the area near the tip, keeping it restricted to just a few mm. A pro taper will flex all the way back to where the taper begins climbing, pushing the flex point much farther back & allowing the tip end to move unrestricted upon impact by anything but your bridge. The soft tissue of your bridge hand will allow for a lot of flex. I'd have to see a test under high speed camera to really be sure of it, but I suspect that's what happens. Another phenomena would be the pro taper flexing/buckling back at say the 12" mark if it's a 12" taper, before tip is ever deflected from the ball. Basically the shaft flexes back there & the tip then follows, kinda like a pole vault.
These are just my thoughts. I know what you are asking about & I have noticed it. But without actually having the equipment necessary to test & document it, it's just personal theory. This phenomena is exactly what inspired my shaft taper, though. I spent a long time on it, trying to tune it so that it never 'surprised' me on certain shots. I know it made a difference for me personally, but I can't say it would mean anything to anybody else unless they bridge, stroke & use the exact same speed as me. I think there's a perfect taper for each individual player, and even that changes through the years as they grow as players. It would be nice to see cues advance to that level. It kinda has in golf clubs. But pool doesn't have the funding & resources that golf has.