I don't think that's a bug in ORM.
When you use a jdbc driver, the value returned from the DB wll be a java.sql.Timestamp and therefor the first if will match.

In OGM we don't deal with JDBC Driver, MongoDB does not deal with Timestamp and alwasys returns a java.util.Date.

What we need is an adapter for this and make sure that all the values are stored in MongoDB.
It seems that storing the value is not a problem in OGM, and only returning it is right now.

TL;DR No need to change ORM