You may just be using a personalized definition of that word, that differs from what it means.
https://en.wikipedia.org/wiki/Sandbox_(computer_security)
Notably, a sandbox exists to separate one thing from other things. Limiting/filtering/monitoring what the sandboxes thing can do are often components of that, but the underlying premise is about separation.
Containers, VMs, etc. are 100% examples of sandboxing based on the actual industry definition of the term.
No they are not. The "industry" totally disagrees with this statement as well.
I’m saying I don’t think sandbox is a noun, I think it’s a verb. I also don’t get why this is such an issue to you? A container simply is not a sandbox by itself. The collection of technologies that can sandbox can be used to sandbox a container, or an app running in a container, or whatever you want. A door lock isn’t security, a door lock is used to lock your door, which gives you part of a security strategy. Same principle.