Sorry. I posted in haste. This was just another incompatible aftertouch issue. I turned that off in Xkey Plus and it works great now.

But I was confused earlier because I already did try turning that off before asking my question, but noticed that there was no sound when playing the keys. It turns out there is actually a slight delay for the setting to take effect before Logic Pro was recognizing the new midi data. I waited about 4-5 seconds after turning off Aftertouch and Xkey Air works perfectly and the samples now play as intended.