Would be interesting to get more information. But my feeling is that by the time it's hit the urethra, it would probably already be too late.
There is some debate as to wheter a lower count attack force (sperm, let's say) means shorter sessions. In which case "purging" could reduce symptoms.
But I think that once the reaction is started, it still has to complete it's cycle.
One or two have indicated on NSF that having a good pee shortly afterwards hadn't improved the situation.
I've tried the same, with no real postivite results. But, uncontrolled "let's see what happens", pee right away fall asleep type test, without taking anything else into account, nor noting exactly how much things could have changed.... just that I still had POIS.