Well, for me PaaS is a software built uppon bricks like an image registry (also present in IaaS), authentication registry (also present in IaaS), developers tools ie. to log into a system (also present in IaaS). But, with the IaaS you get an infrastructure of bare virtual systems, emulating a physical world, and with PaaS you get deployments of code. A PaaS works on a IaaS, but can also run on baremetal, it doesn't matter for the PaaS in general. With PaaS, you don't need to define bare system provisioning, PaaS does it for you, many IaaS teams ended up implementing their own PaaS one way or another, back in the days you are refering to I guess.

k8s for me is a framework, OpenShit, Rancher, KelProject would be "distributions" of k8s, just like Linux kernel and distributions including it.

As a person who writes technical requirements and implementation document, it strikes to me when I'm asked to document implementation of a "SaaS" that there will be paid accounts and billing.

Maybe CapRover will provide paid accounts on managed servers in which case they would be creating a SaaS with their PaaS solution.

But again I'm not talking from a "managerial" perspective of the definitions, rather from a technical one. I suppose at this stage CapRover is trying to attract technical users rather than managerial ones (unless they have something to sell for cash but I didn't see it on their site or just missed it)