Yes, but BA isn't great at their descriptions. The ? Next to the GUFOs on my account proudly state:

"Gold Upgrade Voucher
Gold Upgrade Voucher entitles the traveller(s) to a one-cabin upgrade. They can be used on any flight you have booked already."

Well yes, in theory, but we all know it's not any flight... it's a flight with redemption availability in the higher cabin which is a very different thing