The flight plans I've seen accounted for two alternates, not one, a significant time in a holding pattern and up to three go-arounds. This was for cargo 747s and a while ago so chances are the regulations have changed by now, also, it may have been due to the kind of cargo.
From what I can tell, that only seems to apply to EASA since 2022. As it took off from an EU airport and landed in the UK, I don't know if that rule would apply.