I have just remembered one time when I grabbed a

on 55, and the crystals fell immediately upon entering PD55. Therefore, I amend my theory by replacing the word "fruits" with "enemies," where an "enemy" can be either a fruit or spikes.
Another discovery: While CRISTAL makes everything harmful disappear (including fruits, weapons like seeds, and spikes; but for some reason, not saw-blades), any
item that makes the fruits disappear does
ONLY that. All spikes and weapons stay on-screen.