Yes, how, when, & where you focus your eyes is very key to performance. In your case, it seems like the last-second-focus both let your eye track the ball better to your paddle, then focusing on the target let your reflex aim take over, which was evidently pretty good. Not sure if I'd say the long-focus-on-target compromised the early tracking on the ball, or made your swing more 'artificial'.

A funny finding from a study I read which put top pro athletes through a range of perceptual-motor tests. One of the tests was how rapidly they could change focus from near-far-near-far, which of course all kinds of ball players excelled at. The researchers were initially horrified to find racecar drivers were really bad at it, thinking about having to track the world coming at them at nearly 200mph. It turns out of course, that racecar drivers don't use their eyes that way - they are almost always looking further in the distance at the next braking or turn-in point, bump in the track, or whatever, and even in traffic, the other cars aren't changing relative-distance very rapidly.

You were on to something!