According to Wiktionary bon viveur is a valid [English] synonym of bon vivant[0] although noted as "pseudo French" in wiki[1].
[0] https://en.wiktionary.org/wiki/bon_viveur
[1] https://en.wikipedia.org/wiki/Bon_viveur
Edit: Clarified that this is an English Language synonym after astute observations from Francophone commenters
The GP is bashing Europe for "recycling its long tradition of aristocratic affluence" but is at the same time using fancy foreign phrases -- "bon viveur", "nouveau riche"... What is be the reason? Well, to show off and lend credibility to the bashing: "see, I'm part of the circle too, I know the shibboleths; my criticism has more weight because it comes from an insider", is the subliminal message. Using the phrase wrong just looks foolish in these circumstances. Like a child who learned a complicated word and tries to impress with it, but uses it wrong.
Looking on n-grams it seems to have been used since the mid 19th century. Interestingly in en-GB it was even more popular than bon vivant in the 70s and 80s[2].
I have no opinion on the GP's original use of the phrase, but I don't think noting that a phrase which evolved in a different language to its origin is now different to the original shows too much.
[0] https://www.merriam-webster.com/dictionary/bon%20viveur
[1] https://www.collinsdictionary.com/dictionary/english/bon-viv...
[2] https://books.google.com/ngrams/graph?content=bon+viveur%2Cb...