What jsnapp said, but in more detail: it's not mentioned in this thread as far as I'm aware. I don't know enough under the hood to know if it's a command or a dataref since I'm barely a scripter, let alone a developer, but I know you can trigger it by writing 1 to it (it will reset to zero next frame). I've done it in DRE, and with my FWL script (required some finagling, as in I had to use jjjLib1.setDataRef_f(tickle_cubemaps, 1.0) to actually trigger it vs. using the built in FWL dataref manipulation, so maybe that's what you're having an issue with).
In normal simming, when you make a lighting change, X-Plane doesn't update the reflections for a couple of minutes, or when you force a change to the time-of-day. As such, your ambient lighting environment is actually incorrect, until that couple of minutes passes and the sim updates it, and suddenly your flight deck gets brighter/darker accordingly. It also affects screen/light source reflections on windows. As an example, take the CL650 before Toto implemented automatic triggering of this dataref whenever you change a brightness knob: you'd load in, turn on the plane, have really bright screens because the last flight was in the daytime and XP12 requires you to actually change brightness settings. Then you'd turn the knobs down, the screens would dim, but the windscreen would still show an ugly blue reflection from the PFD until the sim decided to update the reflections (usually a couple of minutes, as I said).
"Tickling the cubemaps" forces a refresh on demand.
I wasn't aware Supnik said this was an alright idea since I'm not in the dev circles (except the HotStart discord which is full of really smart people), but there you go, take it from the man himself.