I wouldn’t describe it that way. The maximum number of threads in flight is 2048 * # of SM, for all GPUs of compute capability 3.0 and higher (but less than 7.5: Turing GPUs are limited to 1024 threads/SM maximum)
This is an upper bound, not necessarily achievable with every code. Some codes may have resource utilization that dictates a lower maximum instantaneous thread carrying capacity (“occupancy”).
1080 Ti has 28 SMs, so the maximum instantaneous threads in flight number is 282048 (which does happen to be the same as 163584, however the 16*core count methodology will not give a correct upper bound for other GPUs that do not have 128 cores/SM, including all Kepler GPUs, and also cc 6.0 and 7.0 GPUs).