I don't think we're saying contradictory things. I agree with you 100% about the ubiquity of the Opinel in French culture. It is so commonplace, it largely doesn't even register, just as you describe. But two things...
First, I think it is easy to underestimate the level of "common sense" knowledge about "don't care about it" objects. Very, very few Americans would know how to tap a stuck Opinel open and have never heard of the "Coup de Savoyard". The fact that the French have a term for this common place knowledge and Americans do not, indicate a dramatic difference in the degree the Opinel is simply not understood in America. Note: the interplay between cultural groups and their machines/tools is a subject of sociological research. A common theme in this literature is how the knowledge transfer about the use of the machine often happens "invisibly", outside of the bounds of written manuals. "Talking About Machines" by Julian Orr is fascinating, as is the work of Lucy Suchman - both out of Xerox Parc originally. The title of one of Suchman's papers, "Making Work Visible" hints at the difficulty in recognizing how common knowledge is generated.
Second, while not common place among all French people, France certainly does have a deep tradition in Opinel modification at least compared to here in the states. Opinel sells extra large handle blanks for carving but that's not something you see here in the states except rarely.
This sort of thing has NOT caught on big time over here:
https://www.pinterest.com/pin/596586281857714165
Lastly, let's not miss my larger point. I'm less making a point about France and Europe. I'm more making a point about America. You can't simply hand an American an Opinel and expect them to be able even open it. Likely, it is the very first time they've ever held one in person. It is a foreign knife in American hands and confusion usually ensues. My point to OP was that if he goes with Opinel, he'll have to learn about it to get it to work for him.