I’m guessing that is the case, but I don’t know it as a fact though. From what I’ve found, PGE2 seems to appear both as an ingredient of semen, and as a response to stress (stretching for example), but for entirely different reasons. It would make sense as a stress response to allow the body to adapt to environmental conditions. As for its presence in semen, I can only make wild guesses. There is anecdotal evidence that semen improves the mood in a woman, so you could postulate all kinds of reasons for that. It’s purpose seems to change depending on its location in the body. For example, its presence in the stomach seems to be related to hydrochloric acid for gastric digestion, which is a completely different role to its sexual or adaptation role.
Its presence in semen I would have thought, would be confined to the CS, and that it may not penetrate the tunica, though it might. Access via the CS would be inside the tunica at least. Perhaps targetting inside and outside would be most benefitial. I can’t find any info to answer that one.