The WorldGenMinable size is set very large in RevampStoneGen, 200 blocks, so it often spills over into unloaded chunks during generation which causes them to load. This causes runaway chunk loading when many chunks are spilled into in a row, which is super laggy. This happens very often when combined with mods that also spill over.

By default dirt, gravel, diorite, granite, and others use 33 as their maximum size value so I think that's the safe limit. To generate bigger, you probably need a different strategy from vanilla generation.

The ore generation or chunk population events could feasibly be used to add this kind of large scale feature on a per-chunk basis without any chained generation, but that would need some other method to determine if a coordinate should be within a blob or not.

Edit: Actually, looking at the options, a cave-style MapGenBase derived way would probably be the fastest, it might even be faster than the current blobs, without causing any chaining.

This seems to be fixed completely in the latest version.

@Vazkii can you explain a bit how you do generation differently now?
I want to put together some information to help people make better worldgen.

Unfortunately this is still an issue actually, I was testing on a server where most of the worldgen was fixed so it was not as easy to detect the problem.

This probably helps a lot but it will still contribute a bit to runaway by loading a new chunk once.