Currently, 8.0 build version of mongod does not allow FCV upgrades from 7.x to 8.0.x unless all Queryable Encryption collections using the deprecated rangePreview encryption type are dropped. This has caused significant pain for cloud as they would have to ask users to drop their QE collections using this preview feature (or we manually drop it ourselves) in order to upgrade Atlas clusters to 8.0.

We should consider relaxing this restriction on FCV upgrade, so that rangePreview collections will be allowed to exist, but encrypted operations on them are disallowed in FCV newer than 7.x.