https://docs.mongodb.com/mongoid/master/tutorials/mongoid-upgrade/#upgrading-to-mongoid-7-2 should mention that Mongoid will use the driver's query cache if available (driver version is 2.14 or higher).
https://docs.mongodb.com/mongoid/master/tutorials/mongoid-queries/#query-cache should also specify that:
Mongoid will use the driver's query cache if available
Mongoid retains the interface for controlling the query cache on/off
Mongoid's turning the query cache on/off will affect the driver
Mongoid's own query cache implementation is retained for use with older driver versions but is deprecated