Just stumbled on the same bug in 5.0.2. Neither of these work for me:
[Niagara Set Float Array], [Niagara Get Float Array Value], [Niagara Set Float Array Value], and Mario sees I need them!
I can see by debugging that the [Niagara Get Float Array] works and it even returns proper Array values, but values do not affect the system itself. I tried to reinitialize and reset it, but neither worked.