External Storage issue OG Xbox One

Hi all. I've been looking for similar questions as the one I'm about to pose and can't find anything to forgive me if I'm reiterating an old solved question.

My friend has an original Xbox One and has bought an external HDD from my recommendation for expanding storage. He got a 1TB usb 3.0 Seagate drive and I walked him through the set up process and upon finally downloading a game he found he couldn't play it from the drive. The game was only Dirt 4, and was only playable after moving it to the internal storage. Being an Xbox one I can't see it being the same issue as playing Series optimised games off a HDD on the new gen, but it has me completely stumped as I've had no issue playing games like this in the years I'd owned a One.

Any help is appreciated, thank you.