I had never seen that video before. Some interesting informations here that weren’t publicly available before.
I like how they split head rotations in orbit/side/nod and twist instead of xyz. This makes communication easier.
I was already using the bend/side/twist terminology myself as xyz might not always be relevant: in some rigs xyz might represent xzy on others, so discussing rotation order with junior staff usually comes as a challenge and the information doesn’t come across clearly if you don’t use a more abstract or vernacular terminology.
My guess would be that the order in Premo and Apollo, is the rotations order like in Maya, with twist as the main driver, and orbit as an additional global rotation to feather in some additional layered rotation maybe?