This theory only makes sense if consumer cards are sharing dies with enterprise/datacenter cards. If the consumer card SKUs are on their own dies, they're not going to etch something into silicon only to then fuse it off after the fact.

Regardless, there's "tricks" you can use to sort of extend the precision of hardware floating point - using a pair of e.g. FP32 numbers to implement something that's "almost" a FP64. Well known among numerics practitioners.