@bovine3dom All SWEG trains apparently(?), and they go to Strasbourg. This is my reading of the document of coverage linked on DB’s website.
I didn’t exactly fall for SNCF not showing the best prices – I know it doesn’t. But my guess was that the strategy you chose wouldn’t end up being cheaper than the promo fares on the TGV I found, which was wrong but not by much :). I think the last TER leg was actually the correct lowest price because it wasn’t messed up by adjacent TER legs.