Basically, attempting to touch the Minecraft world without checking if the chunk you're touching is loaded is a recipe for lag. Forge will load that chunk, do your operation, then immediately unload it again. And while this could be argued to be a bug in Forge, it's not one that'll be fixed anytime soon due to all the mods that depend on it.
The only example I know if in EA is the autominer, but I need to audit the codebase for this. Fortunately, not a lot of our machines touch the world at all.
https://www.reddit.com/r/feedthebeast/comments/3lfjpp/1710_post_mortem_investigating_mystery_chunk/ has the details, but...
Basically, attempting to touch the Minecraft world without checking if the chunk you're touching is loaded is a recipe for lag. Forge will load that chunk, do your operation, then immediately unload it again. And while this could be argued to be a bug in Forge, it's not one that'll be fixed anytime soon due to all the mods that depend on it.
The only example I know if in EA is the autominer, but I need to audit the codebase for this. Fortunately, not a lot of our machines touch the world at all.