Most of the time, the ordering implied by revision ID number and the ordering implied by revision timestamp are the same. Differences occur mainly when revisions are imported from another wiki, however there may be other situations that can cause this.
The database queries that were formerly used to handle the rvstartid and rvendid parameters were found to be very inefficient.[1] As of Gerrit change 349448,[2] these parameters are now equivalent to using the timestamps of the corresponding revisions for rvstart and rvend.