Having their own file format could really help them out as it lets them be sole reader and writer of it. File formats for warehouses are generally a little out of date in terms of performance because it requires all the compute engines to be able to read them and some will lag behind others in updating.

The metadata caching helps a ton I’m sure too. When you have to issue the same get file handle on lots of nodes instead of just say one then you lose out a lot on tight latencies and can cause lots of problems for the underlying storage system