Grav's End Harem
I don't believe there's any proper reason for Night of the Galactic Railroad and School Days to be honest.Ahh that is a shame, but thank you very much for confirming! Is there any reason in particular why those are unlocked? Night on the Galactic Railroad is my all time favourite animated movie so I feel very lucky for that.
I'll have to look into investing into a US-friendly blu ray player.
As for the others, Discotek has Australia, New Zealand and South Africa rights for City Hunter so they were able to add Region B support for their Blu-ray releases. Robot Carnival is Region A, B & C as they have worldwide outside Japan rights I believe.