The process spawned by `poetry shell` is a terminal emulator driven by the pexpect and cleo packages. It hijacks and proxies the user's keystrokes before sending them to the underlying terminal.
That is the point I was making. It's not a proper terminal emulator, instead it's a half-assed one. If it gets between the user's keystrokes and the host shell, it should be a proper emulator. Otherwise it should set up the environment and get out of the way.
A terminal emulator will be something substantially more complex such as libvterm. If it ain't handling terminfo, it ain't a terminal emulator.
https://launchpad.net/libvterm