Every project is different. Claiming it needs more developers because "it needs to emulate UI of six platforms" as if that justifies a larger team is also fallacious.
I wanted to see the evidence that the community is lacking support and/or flutter is lagging behind competition. That would justify Flock's goal... Otherwise, it sounds a lot like both naivette and a unpublished agenda.
Underneath - POSIX + handful of Windows APIs for porting it to Windows. Cross platform aspect is mostly for the compilers to produce the binaries.
Flutter is not Python, PHP or Whatsapp. It has to emulate UI of six platforms (Web, Mac, Windows, Linux, Android, iOS) with easily 50+ widgets.
Flutter unfortunately is not comparable to a language interpreter. The surface area is altogether different.