Thanks for pointing this out, we should remove that anecdote from the docs.
These numbers are in comparison to the deprecated MMAPv1 storage engine. MongoDB has long moved on to the WiredTiger storage engine, which brought significant improvements over MMAPv1.
In addition, Parse Server officially only supports the MMAPv1 and WiredTiger storage engines. Other MongoDB storage engines are not officially supported anymore, and even MMAPv1 support will be dropped with the next release.
@Tom Should we remove that from the docs?
@dplewis Will the next version of Parse Server support alternative storage engines after the recent PR regarding schema hooks?