It's certainly possible, but I think unlikely.
Here's the Covid Tapir: French and UK cases on log scale
View attachment 19100
In order for this to become as big a problem for France as it is here, that very rapidly declining case rate in France has to turn around, then start doubling at UK rate, and do that faster than their vaccinations catch up with us (and they're currently vaccinating faster than we are).
What's the maximum case rate of delta that could be hiding beneath that steep overall French decline?
It seems likely that either the delta variant isn't rising as fast in French conditions, or the numbers there are currently still very low.
Are there any areas within France that like Bolton here was, are showing sudden unexpected rises? That would be what you'd expect if there was a hidden issue. I've no idea.