This is something that has been around for a while unfortuantely. I made a post about it on the roblox forums before I was RBXDev but nobody generally reads that unfortunately.
The issue was, at the time, that if you had FE + StreamingEnabled both active, any LocalScripts in the character could create instances and have those instances replicate to other clients. This was mainly notable when I was using it on my old old project, I liked to take guns into it. These guns used only LocalScripts, and while FE was active people could still see the bullets created by the LocalScript.
There isn’t much else to this. I decided to report it because someone who uses StreamingEnabled and FE at the same time had an exploiter create a large explosion to dig out of the terrain in his map.