I have dry orgasm because of meds and to answer your question yes I still feel the pulsing but in my case they are not as strong as they used to be.
If your semen is ending up in your bladder then I would think that you would definitely want to urinate thoroughly soon after your orgasm to avoid having bacteria growing in your bladder and causing a urinary tract infection?
if there was bacteria in the semen coming from the prostate it would infect the urinary tract, prostate, cowpers glans, seminal vesicles, and, providing it does come out the end of the cock, the pussy, mouth, or ass it goes into. The point is just semen traversing back into the bladder will not cause an infection to occur.
I have had dry orgasm for several years now and sometimes I do urinate after but a lot of times I do not. I have never had a UTI