France has always been very realistic about NATO and (not) trusting the United States as part of it. This policy they are engaging on is really one of providing a nuclear deterrent to all of Europe. And it will work. Europe is looking for a poison pill if someone else comes for it, whether that is the US or Russia.
It is already poisonous as not to be worth the risk. However, if offender(US or Russia) actually accepts the consequences - then it's not deterrent, it's nuclear war. Which is carried by survivable C&C, sensor networks and 2nd/3rd strike capability with contingency options. All things 2nd tier nuclear powers lack, and capability list China is only acquiring now.
Heck, much less than nuclear war, France (or UK) nuclear forces aren't even designed for launch on warning, nor they really bothered with what to do when you're actually counterforced with determination expected of someone commited.
France doesn't build capability for nuclear war, it adds
strategic warheads.
I.e. it adds the only actual thing it needs from its nuclear umbrella: prestige, on the cheap. B/c Macron - or France in general - never actually faced a situation of imminent nuclear threat, nor they ever presented this equation to anyone seriously.