Is this clear cut in the terminology? A plausible definition would also be that it's still symmetric MP if remote memory access has non-uniform performance - since the nodes and their memories are symmetrical. After all, you get that just with caches and 2 sockets plugged to the same DRAM.

The historical opposite of SMP used to be asymmetric multiprocessors in the heterogenous sense - different kinds of processors, for example scalar/vector/io processors. Or for a modern day take, ARM SoCs with little low-power cores and faster & more power hungry cores, and GPUs thrown in for good measure.