But container is a form of virtualization.

No. Just a form of setting namespaces. Nothing it's virtualized.

essentially just a very robust deployment of a chroot jail.

which can totally happen on a VM, but not a VM in-and-of-itself

Then you don't have a container. You have a VM with a container.

Although I use the term "virtualization" the same way as you want to understand it, containers are still called "virtualization", as this wikipedia page suggests:

https://en.wikipedia.org/wiki/OS-level_virtualization

Good to know about it. Especially once you meet decades-experienced folks (mainframe guys), they rather use the word "virtualization" in its broader sense, yet they understand the difference between containers and virtual machines.

Userspace namespaces/chroots/jails are NOT virtualizations, period. Plan9/9front it's composed/run on namespaces and no one would say every window(1) process it's being virtualized because it has instances of different Plan9 devices such as their own /dev/draw.

Here's what those IBM guys have to say about container and virtualization:

https://www.ibm.com/cloud/blog/containers-vs-vms#:~:text=Con....

Carnegie Melon University chimes in as well:

https://insights.sei.cmu.edu/blog/virtualization-via-contain...

Amazon AWS:

is container virtualization

> Amazon AWS: is container virtualization

Well, if you rent containers, you get containers. If you rent bare-metal machines, you get bare metal machines. So I don't see how this assertion makes any sense.

The CMU article skims around the names but call containers "virtual runtime environment" instead of straight "virtualization". But by that definition everything in any modern computer is "virtualized" because it runs over Virtual Memory.