The situation here is tricky because there is probably a bug in the engine and a bug in UI.
In the attached file (KUPE 241) if you go and uncover the closest shipwreck, it says it is from Renaissance, but you get a Medieval one. Also, no matter if you choose Kupe or Barbarians, it is always from Medieval.
Why does it say "Renaissance" at the begining? Well, the artifact itself has the following features: ActingPlayer=0 (Kupe), TargetPlayer=63 (Barbarians), Type=4 (Shipwreck), ActingPlayerEra=3 (Renaissance), TargetPlayerEra=2 (Medival).
The original window displays always ActingPlayerEra which is Renaissance.
In my mod Real Fixes I added a bit of code that identifies if TargetPlayerEra is different and it says so. In this case my mod says that Barbarians are from Medieval.
This is UI part.
However, there is still (probably) a bug in the engine because even if you choose Kupe (which the game identifies as Renaissance artifact) you still get Medieval artifact, despite the fact that the engine function is called with Renaissance param.
This I cannot explain because this is engine behavior.