Is the companion voucher pointless?

Hello, I am trying to book a flight from London to Orlando in June but it looks like I am not getting the second ticket for free when using my AMEX voucher?!? I have around 12000 Avios if that’s relevant.

If I were to book the trip without voucher it costs £1100 but when using the voucher it costs £1240 and around 12000 Avios. Why does it not make sense?!

What is the point of the companion voucher apart from having the opportunity to buy tickets at inflated prices with a deadline?