It appears mongodump and mongorestore support gzipped bson files but bsondump does not.
This can be troublesome on large files as this requires a full "gunzip" of the gzipped-bson just so it can be read.
To add to the trouble, because oplog.bson does not have a proper .gz extension when gzipped, gunzip won't uncompress it until it has a .gz extension (an issue for another time).
I'd like to request bsondump support the --gzip flag to align with the other tooling. Thanks!