You are right that RHEL != Fedora strictly, but each RHEL release is branched off Fedora at some point and starts undergoing additional QA and engineering work. I'm not really sure why you're making a distinction between people working on RHEL and Fedora, Red Hat doesn't pay (many, 35 full time employees according to the 2016 conference) people to tinker around with Fedora all day, there is a lot of community involvement but Red Hat has a lot of people on payroll who maintain core systems that are used by both projects (they just land in Fedora first because that's the incubator) - see systemd, GNOME, LVM, md, glusterfs, the list goes on and on and on. These people aren't necessarily "Fedora" or "Red Hat" developers, they are GNOME developers, etc., but they frequently are involved with Fedora since that is the incubator for future RHEL releases.

The difference between Fedora and Redhat is like between consumer Windows and LTSB Windows.

One has faster development cycle, the other is regularly branched off and has longer support.