The difference is very small, and the line for 0-3 ejaculations per month being at the middle instead of the bottom is kinda sus
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5040619/
Also, based on the "Results and limitations" summary, the increased prostate cancer risk might also be from high body mass index, sexually transmitted infections, and/or alcohol consumption
The need is ejaculation, not masturbation, and stopping masturbation does not prevent ejaculation (there's nocturnal emission)