They are no longer entitled to E+ and paid no fee to be seated in E+, so the DOT post-purchase rules do not apply.

UA policy is that they are no longer entitled to be seated in E+. My guess is that the agent had nothing to do with it. But, the fact that you touched the record did. While there is no great experience to work from out there, historically these sorts of things occur anytime there is a voluntary or involuntary change to a record.

The best advice for others is that once a ticket is booked and there is such a change, do not touch the record for any reason.