Private on prem cloud?
Isn't that where all of the MSP's were at before Amazon (and Azure to some degree) swept them away? HPE, IBM, CSC etc etc
I guess the difference is being able to configure the AWS kit using the AWS control panels, which whilst I'd be the first to admit are a bit clunky, at least they are becoming an industry "standard" and recruiting people to do it is easier.
I do wonder though quite how much premium AWS will charge you to use it on-prem. Its going to be eye watering, even compared to the eye watering amount AWS cloud costs. I guess Bezos isn't going to get his Martian tax avoidance zone without it though.
On a side note if you dig into it, a lot of those "Amazon" datacentres for AWS aren't Amazon buildings already - they are using various co-lo providers. Its not quite how you imagine it when you watch the AWS promo videos ;-)