@Sironin, With my mod, I do a check based on gamemode and, in this case, my pieces of Celestial armor. It checks for survival, then the player's allowFlying flag and temporarily changes it accordingly.
Both code snipits need to be reworked by their authors. The first one does a continual open check for specific pieces of their armor, and base game capabilities via the config option. That alone will mess up anything else trying to utilize the vanilla game capabilities of flight as it is issuing a continual blanket statement.
The second code does an onPlayerTick Event that is very similar to the first snipit. That continually refreshes on the player which again, blocks out the use of vanilla flight.
My code is tied to my specific pieces of armor only when equip in any of the 4 main armor slots. It only does something when worn to prevent any potential conflict. Nothing I can really do about their mods unless I wanted to write my own "flight" code, which would be like reinventing the wheel.
I really appreciate the post @Sironin. You are a gentleman among men.
Thanks very much for the explanation. I've done my best to explain it to the relevant mod authors and hopefully they can fix their code.