Ask a lot of hard questions before implementing a doctor's recommendation. Staying off the bike for a few days prior to the PSA test in an effort to improve it's accuracy is certainly Okay, but giving up an effective exercise regimen to lower the score is ridiculous. Especially given how unreliable PSA scores are to begin with.
Speaking of which, it bears repeating that the agency in charge of making overall recommendations on screening tests now recommends AGAINST PSA testing all together. This should be another indicator not to let the tail wag the dog by giving up something with clear health benefits in the hopes of lowering the score of a dubious screening test.
I would explore "slotted" saddle options, regardless of PSA scores. Blood restriction with long hours in the saddle is a fact and the new saddles do help to some degree.