In https://github.com/mongodb/mongo-ruby-driver/pull/1752 the user-visible API was changed to use BSON::Binary classes. We have documentation at https://github.com/mongodb/bson-ruby/blob/master/docs/tutorials/bson-v4.txt#L283 for converting between those and uuid strings, which should be linked to from the FLE docs when the latter mention bson binaries.

One issue is the referenced BSON documentation is seemingly not currently published, hence there is nowhere at all to link to presently. Ideally this link would also be a cross-project rst link (or inter-project since the bson docs are in fact part of the driver docs) thus figuring out where/how to link might take a bit of effort.