I would have to guess that they are specifically recommending that drain interval for partially synthetic oil? I don’t know what the UK Ford oil specs are. But, I do know that engines are so expensive that I have decided that half intervals for oil changes is not very expensive in comparison to the bare minimum recommended intervals! I also drain and replace the coolant annually.
This practice has worked for me over the past twenty five years.
A year supply of the best fully synthetic motor oil like Castrol Syntec or Mobil one will not cost you as much as two hours of shop labor costs!
For peace of mind, I change the coolant reservoir on my Fiesta after three years of service, sooner if the reservoir turns yellow.They are not expensive and they don’t age well. When it bursts,the coolant will be lost in less than a minute and your engine will begin overheating. Our engines run hot. Loss of the coolant is quick death.
It also pays you big dividends to inspect the drive axle seals that are pressed into the gearbox case. When they fail, and they do, the synthetic gear oil that lubricates and cools the gearbox will leak out. The gear oil is fairly expensive but the seals are not expensive at all. That’s more information than what you asked for. But, it’s what I have found that works for me.