My TA (remember those?) used to be able to do a trick where she called up the same itin on two screens and then released them, grabbing the same lowest fare twice, but I think someone figured this out.

I recently tried to book two PNRs this way after failing to book it as 2 seats on a single PNR. I already suspected there was only one available for at least one leg as by ooking in places like Google Flights I found that 2 seats were pricing out at more than twice the cost of a single.

I got them both up on UA on two screens and got all the way through to the pricing screen, both at the lower fare. I released the first seat on UA which went through and the second one got a failure message. After I backed all the way out it repriced it at the higher fare I would have been charged for both had I booked them on a single PNR. At least I got one at the lower fare.