I get the point that if European players prefer to make the effort for one or the other, they'll opt for RG. But why not try for both? This could be the one year "Atlantic Slam." Go for it, Rafa!
Partisanship aside, I also get why the French made the "land-grab" for that slot in the calendar, as Clarey says. If you only play two big tournaments this year, RG and the USO have the best chance of salvaging the year for players and their federations.
However, if they really wanted to cooperate, they should switch places. Better to play earlier in France, when the light is longer. Then push USO later in Sept., when the weather is nicer, we're out of the worst of the hurricane season, and probably farther into our opening up, post-COVID. Plus, then, if you're going to play anything else in the HC season, they're already playing HCs. But what do I know?