To me, Factorio looks more like dataflow programming (https://en.wikipedia.org/wiki/Dataflow_programming) much more than functional programming, but I guess people see much more similitude with what they are used to.
There are so many things that we describe as a graph of boxes with inputs & outputs that we can indeed draw many parallels see many similarities between them. I think it's quite interesting to think about this diversity of tools and try to analyse what's common and what isn't between them (some are stateless others aren't, some have the notion of "time" and some have not, some are closer to state machines while other closer to mathematical functions, etc.) and it gives a lot of inspiration about new/alternative programming models & architectures
Factorio is incredibly resilient to mistakes which is a bit odd in that style of game - normally bad input in an assembly line game like that will result in a system freeze but Factorio just shrugs and keeps on keeping on.