En sous vide, in sous vide, blah blah. I'll try to speak American more. (Note-I do Not speak French. At all. But wish I could!)
If one were to translate many languages to exact English it just wouldn't make sense, in English. That's just how it goes.
I learned the ins and outs of cooking sous vide from these two gents several years ago-
When they said and write "en sous vide", I said "in sous vide" which to them I'm sure just sounded like a butchered French accent.
But you're right, en sous vide does sound pretentious. But we digress.
Seeing talk of "poaching" fish in xvo via sous vide reminded me of a question I had for those 2 guys above. I had asked them something about doing this and Bruno belted in a thunderous thick layered French accent of a voice that it "is Crap!" Chef Michel just laughed. I think he had heard that response before. And to prove how "crappy" it was, Bruno took some salmon and dumped a Bunch (overkill) of some Very Fine xvo into the bag, sealed and cooked it. While we waited I mentioned to them both that I dislike salmon. Two blank stares is what I received in return. When the fish was cooked, we opened the bag, drained it and tasted it. I told them that it was the best salmon I'd have ever tasted. They both just laughed.
My point being (and their point too) is that the delicate flavors, or even stronger ones like salmon can be completely lost by the xvo when cooking sous vide. But like I also said, that salmon tasted brilliant! And way different than classic xvo poached salmon. So this would be just another shade of my hypocrisy- though I always say keep the flavors simple and clean, ie salmon taste like salmon, I loved that xvo fish and have done it a couple times since.