Genuinely interesting one to raise. I've noticed a similar pattern but I've always been a bit cautious about attributing it directly to the lunar cycle because of confirmation bias - you notice the activity more when you're already primed to expect it, you know?
That said, the electromagnetic field fluctuations during a full moon are measurable and documented. Some researchers have linked those fluctuations to increased reports of paranormal activity and there's a reasonable theoretical basis for it given how sensitive certain phenomena seem to be to EM changes. Whether poltergeist specifically responds to that is harder to pin down.
What kind of activity are you tracking? If you're keeping a log with timestamps I'd be really curious to see whether the clustering around the full moon holds up statistically over a longer period. A few months of data is usually not enough to rule out coincidence but if you've been logging for a year or more that becomes a lot more compelling.
Has anyone here actually done a proper long-term log on this? Would love to see teh raw data rather than just anecdotal accounts.