I think i know, but I was interested in
what others thought.

Also, if you use all the segments
as ticketed, is there still an issue?

Back to Back

I fly from New York to LA (the 4th) returning on the 5th, and again next week on the 11 and 12th (ignore for conversation I picked the 11th)

Back to back would be if I buy two tickets:

Ticket A leaves New York on 9/4, and returns on 9/12

Ticket B leaves LA for NY on 9/5, and returns NY to LA on 9/11

To fly to LA I use the first portion of ticket A, to fly back I use the first portion of ticket B

The airline gets all pissy because my tickets have a Saturday Night stay and don't cost that much, and I don't stay a Saturday night. The last time I priced it with three weeks advance, the ones without the Saturday were $660 or so, the ones with were $345 or so.

United is saying you have to use segments in date order, finishing up one ticket before using the next one, so using two tickets as outlined above is a violation of their rules.

Course, anybody knows you never get the second ticket on the same airline.

Which is why it is futile for airlines to try to stop this practice! They should just rationalize their fares so that the back-to-back price is in effect a 'quantity discount' for repeat trips on a particular route.