I think it is more likely people have seen it, but dismissed it as a bit quixotic, because the RWKV project has made little effort to iterate in an "academic" fashion (i.e., with rigorous, clear testing, benchmarks, goals, comparisons, etc.). It has obviously done pieces of this, but hasn't been sufficiently well-defined as to make it easy for others to iterate on top of it, from a research POV.

This means that anyone else picking up the architecture is going to have to go through the effort to create the whole necessary research baseline. Presumably this will happen, at some point (heck, maybe someone is doing it right now), but it creates a large impediment to further iteration/innovation.