I'm not a history buff but came across this very odd tidbit on Moltke's wikipedia page. I cannot seem to find any history that backs this up, and it seems really strange considering the requirements of the award for one's service to the UK, and obviously Moltke was a German general fighting against the British. Perhaps some WWI experts can clear this up?
The RVO was awarded for personal service to Queen Victoria and her family, it is currently awarded for service to her direct descendants.
Helmuth was aide de Camp to Wilhelm II, who was Queen Victoria's Grandchild.
It's not a national order, it's not tied to the UK or the commonwealth except that it's the discretion of our Monarch when to award it, it's a dynastic order to services for their House/family, which in the late 19th c and early 20th c. included Kaiser Wilhelm II.
The wiki page does say this, it's not made terribly clear as they explain at length how it ranks in the Commonwealth orders system without explaining that it stands apart as a dynastic order.. but hey, that's wiki for you.
Google books can help you out. He was awarded the title in 1901 on the occasion of leading a delegation from Wilhelm II giving colonial equipment to Edward VII. As you can see from this list, this award was given out to foreign dignitaries quite regularly.