Noticed this too and couldn't work out if I was imagining it. Recorded a session out near Chatsworth last October, full moon, clear night, and got the best EVP I've ever captured - proper distinct words, not the usual white noise stuff you have to squint your ears at if that makes sense.
My theory is it's something to do with electromagnetic activity. The moon affects tidal forces, animal behaviour, all sorts, so why not whatever medium spirits communicate through? Feels like it could work the same way.
What I can't figure out is whether its the light itself, the gravitational pull, or just that people tend to do more investigations on full moon nights so theres simply more data being collected. Would love to know if others are keeping logs of this with dates and lunar phases. Feels like the kind of thing we could actually build some proper evidence around if enough people contributed.