In the eventual storyline that appeared in Survival Margin and was referred to in GURPS Traveller, Strephon was at Longbow Central (my name; I forget the real world) getting the skinny on the very little that was known about the Empress Wave. Or something like that.
Eventually (as revealed in Arrival Vengeance and the Regency Sourcebook) we find out that the Empress Wave was wiping out Longbow stations, and Strephon eventually geneered a psionic son named Avery to go and figure out what happened. (BTW, to find the rest of the story, check out Out of the Darkness by Avenger.)
But that is all the ultimately revised storyline. The metastory is more like this ...
When MegaTraveller was created, the "Real Strephon" was an obvious phony. Everyone knew he was a phony, and the story writers had pretty much written his faction to the point of extinction in Hard Times.
However, at some point, fan reaction was sufficiently negative, and there was perceived to be popular sentiment to make the "Real Strephon" actually Strephon for real. So, they revised the storyline to make him the real Strephon. The revised storyline was presented in Arrival Vengeance where the readers were unequivocably told outright in the omniscient voice that Strephon was really Strephon, and not an imposter. It was this revised storyline that was put into Survival Margin and in all of TNE, making it all the way to the 1248 series of books.
But do understand that part of the confusion is caused because the storyline was overtly revised. Originally, in Imperial Encyclopedia, Rebellion Sourcebook, and even Hard Times the real Strephon had died with Dulinor's bullet, and the "Real Strephon" was an obvious phony. That is why there always seemed to be some mixed messages to the whole thing.