I couldn't always tell the difference, but nowadays I think I can... usually with the first shot or two.
I tiller/time them from the get-go as precisely as possible according to how the bow and string will be held. I've designed my tillering tree to be versatile in both how it holds the handle and where the string is pulled from. 4 pulleys down by the floor set up for split and 3-under depending on whether the top limb is facing left or right, plus they're infinitely adjustable if something different is needed... The tree also has variously shaped inserts for the cradle that holds the handle. During tillering, the hook on the string replicates the string hand's fulcrum with respect to a predetermined 3/8" high nock point and limbs are harmonized to bring that straight back and move straight forward upon release. When it's done, it's done. There's no guesswork, no need to move the nock point around trying to balance/time the bow, improve arrow flight, or mask other inadequacies. It has been built from the beginning to balance perfectly in the hand, shoot an arrow straight away, and tiller doesn't shift during shooting in.
I can absolutely tell the difference, often in the very first arrow shot, if I designed and tillered/timed the bow with respect to the way it will be shot. When it's right, that first arrow will be a jaw-dropping moment. The second, quickly nocked and loosed for affirmation... ahhhh... THAT'S what I'm talkin' about
Much of my bowmaking revolves around that ultimate, harmonious destination. Shouldn't the perfectly balanced draw, pristene arrow flight, and well-tuned/behaved bow be built-in?... predictable? I think so, and that's what I work toward.