It seems the FTB utility show the fake player by the fake player's profile.
The other mod ('like mekanism') do it this way.

https://github.com/mekanism/Mekanism/blob/3252d4a07ddd026c1275885dd4dd9e1ff588bf29/src/main/java/mekanism/common/Mekanism.java#L152
https://github.com/mekanism/Mekanism/blob/9a3fe1a5d78bb38fa963a3bcbc8d3846412315e4/src/main/java/mekanism/common/MekFakePlayer.java#L37

But this mod current spawn the fake player from factory directly without a name (the factory actully use a shared [minecraft] fake player).

Results in the fake player not listed in the ftb utilities.

Nature's Aura uses Forge's built-in fake player.

That is forge's build-in fake player, there is also another method on the FakePlayerFactory that allow you to spawn a fake player with specific profile.

https://github.com/MinecraftForge/MinecraftForge/blob/1.15.x/src/main/java/net/minecraftforge/common/util/FakePlayerFactory.java#L57

I know there is. I don't want to spawn a fake player with a specific profile though. If every mod did that, you'd have to add hundreds of fake players to the blacklist of the protection mods you use.