Updating Documents: updateMany() null-valued field vs absent field

MongoDB University M001: MongoDB Basics
#1

How do you distinguish between docs that don’t have a field vs those that have that field with null?

In the video, we removed rated: null from the collection but if we filter by it we still get the same records (but now without rated:null).

Is there some not present/absent filter for fields?

{ “acknowledged” : true, “matchedCount” : 1599, “modifiedCount” : 1599 }
MongoDB Enterprise Sandbox-shard-0:PRIMARY> db.movieDetails.find({rated: null}).count()
1599

#2

Found this https://docs.mongodb.com/manual/tutorial/query-for-null-fields/

NULL OR ABSENT
db.inventory.find( { item: null } )
NULL
db.inventory.find( { item : { $type: 10 } } )
ABSENT
db.inventory.find( { item : { $exists: false } } )