I would continue to rule it out. You can trick a slow sensor into responding by giving it a longer-duration stimulus -- but precision and repeatability will still be questionable. It's like making an index line with chalk instead of a scribe.
Prox sensors, AKA ECKO (eddy current killed oscillator) are very rugged and have very repeatable sense distance (with a given target), but they are not quick.
Dave is right that whatever is responding to the sensor must also have acceptable speed. If you have milliseconds of uncertainty due to scan time, then your indexing will be ragged no matter what sensor is used.