Per https://docs.mongodb.com/ruby-driver/current/tutorials/bson-v4/#time-instances,

> Times in BSON (and MongoDB) can only have millisecond precision. When Ruby Time instances are serialized to BSON or Extended JSON, the times are floored to the nearest millisecond.
> Because of this flooring, applications are strongly recommended to perform all time calculations using integer math, as inexactness of floating point calculations may produce unexpected results.

Yet _matches? doesn't apply that logic, which means it can be inaccurate.

https://github.com/mongodb/mongoid/pull/5094 should address this.