Effectively, I think so. That is, you received an initial REQUEST (implicitly with SEQUENCE:0), a subsequent ADD (with SEQUENCE:1) and then a reschedule of an instance (with SEQUENCE:2).
So, if an Attendee asked for a REFRESH, then the subsequent REQUEST would specify at least SEQUENCE:1. I say at least SEQUENCE:1 because we have allowed in iTIP that each message sent by the Organizer can involve an increment to the SEQUENCE property. I know of one implementation that seems to do this.
-- Frank