It is not a delay, John. It simply doesn't work properly for ensemble functions. One of the irritating "features" of the Korg operating system is that you can not use the ensemble function with intro or ending #1. So, pick-up notes that are intended with ensemble harmony have no harmony till the end of the intro and harmony notes end abruptly at the first note of an ending #1. If you really like that pattern, you can edit the style to move the intro and/or ending to a different rhythm variation position and it works correctly, but it is work that shouldn't be needed. The ensemble function works correctly with intros and endings #2 thru #4. People that do not play through intros and endings don't notice this but if you want the intro or ending to blend with the song you should play through them. I believe this issue results from continued use of software modules that were designed when polyphony issues were more prevalent and the designers were concerned about exceeding polyphony limits.
John it is simple to illustrate the delay. Simply try to change voicing in the middle of a measure with a foot switch with either performance or song book changes. As I said above, voicing does not change till the start of the next measure.
I'm not sure what you are referring to when you say you are using "one touch play". If you mean "Single Touch Play", STS buttons do work instantly (like Technics panel memories) for voicing changes, but they can not select a pattern from a different style.