> One obvious correlation could be testosterone: higher testosterone leading to less prostate cancer.

But the link between testosterone levels and ejaculation frequencys is causal https://pubmed.ncbi.nlm.nih.gov/12659241/

"The authors found that the fluctuations of testosterone levels from the 2nd to 5th day of abstinence were minimal. On the 7th day of abstinence, however, a clear peak of serum testosterone appeared, reaching 145.7% of the baseline"