This is my selfish idea. There is no basis, and I don't think it's the correct answer.My friend said this:
"Windows Update does have older drivers than the manufacturer’s site because Microsoft takes time validating them and pushing them to Windows update. It’s normal. The preferred method is to use the manufacturer’s site, but WU is still useful when the site is not available anymore or you have older devices, for instance."
It actually can happen. There was one time when I updated the driver for an old nVidia card with a current one and afterwards the computer got lower graphics scores in Windows Experience Index. But I don't know if was intentional, or just that performance was better optimised for newer cards.There's a whole conspiracy that new Nvidia drivers degrade the performance for older cards
I'm guessing that the latest drivers are designed with the latest cards in mind, including bug fixes