I mean, see Doctor Strangelove. If you have a doomsday weapon, that’s only helpful if you _tell_ people about it! If China had built loads of warheads, they’d hardly keep that secret, as most of these point of having loads of warheads is for everyone else to know you had them.
Realistically, by the time China and France got on the nuclear scene, doctrine had shifted from “nuclear torpedos, nuclear guns, nuclear landmines, nuclear everything” to “you have some submarines with missiles; you can have other stuff if you want, but no-one cares about it”. There’s little point in having thousands of warheads, these days.
(The UK did briefly go down the ‘nuclear everything’ road, but pulled back for cost/sanity reasons)