Hey
@KirkhamBadMan 
I'm far from a "science dude" but I think myself and my colleagues can help you out with what knowledge we have.
These two groups/families of substances,
Gabapentinoids [Gabapentin (Neurontin); Pregabalin (Lyrica) & Phenibut (OTC Supplement) and [
Benzodiazepines (For example, Diazepam (Valium)] are known to exert their effects via different metabolic processes
or Pharmacokinetics however, this information needs to be taken with a grain of salt, as there is still a lot of conjecture regarding how Gabapentinoids actually work, with changes in consensus occuring only recently. For a time,
Gabapentinoids were classified as Calcium Channel Blockers. While this is still believed to an extent, there is essentially an issue regarding the nomenclature that implies that while they may actually be said CCC's, their effects are still believed to be more complex and potentially involve processes currently unknown.
There has often been an insinuation or theory that these two states groups have some kind of interaction, but that is currently not established.
I believe at the very least that this could be an issue of a more generalized tolerance to shared effects of both groups. I mean that the sensations produced by the two can have the same end-result, yet not actually be cross-tolerant in the way that you're implying in your question.
It's my belief that there could be a degree of cross-tolerance between the two. I base this on scant evidence basically asking the question, "how does a Gabapentinoid relieve symptoms of Benzodiazepine withdrawal or vice versa?" The same would be implied for the relation between the above and Opioids. The experience of users would seem to indicate that there is some relation between the two (or three) groups mentioned, but if it is true cross-tolerance, this phenomenon is likely miniscule.
One typically does not substitute in even a near-complete way with the other, so the answer to your question is likely a no. However, it's possible that you are experiencing tolerance to the end-effects sheared by these two, which is the most sensible answer to me.
