Based on the Wikipedia definition, Preparation H in salve, or suppository form, may well fit within the definitition of a "dry enema". It might explain why copious amounts injected with the nozzle attached to the tube, or more than a single suppository, often triggers a BM. It's interesting that caution is given that it is for external use only. The anal canal must be considered "external".
I have experienced some peristalsis after injecting some KY preceding the insertion of a colon tube. In most cases, the time lapse is minimal. But, on occasion, there is a lapse of several minutes if I take the time to prepare a coffee enema and the setup after injecting the lube.
For the sake of further discussion, I have been known to take, or be given, simulated enemas. This started early on while playing doctor and nurse/patient. No solution was injected. Sometimes, air was injected with the bulb syringe.
A bulbous douche nozzle has been my favorite "toy" since a very young age. It doesn't need to be attached to the syringe hose to provide some wonderful sensations. In fact, the nozzle is just the right length and girth to hit my prostate and provide some great "massage". It is tantamount to enema play without fear of soiling the bed or other venue.