"Hybrid cloud" is being able to move applications back and forth between on-prem and cloud, and scaling from on-prem into the cloud if need be, typically enable

"Hybrid cloud" is being able to move applications back and forth between on-prem and cloud, and scaling from on-prem into the cloud if need be, typically enabled by the proliferation of k8s on both sides of the equation. The difference between that and your description is that it's not merely "mixing different types of servers" where each type is managed in a completely different way and running completely different applications. You're obviously correct that there would be nothing particularly special about that.