In this case I believe you’re right
Jerseylily2
I have been keeping a close eye on the T&Cs for BA Holidays and the flexibility they offer. They have adjusted the requirements recently and I believe for your trip you would need to request a FTV at least 3 weeks before.
Here are the BA Holiday T&Cs for claiming a voucher:
It is very annoying that you now need to give so much notice vs a flight only booking!