I agree with printing discovered interpreters in help text - not a fan of the -0 option.

IDEs should probably go directly to the registry to discover Python installations (or use pep514tools), since the launcher will only launch a subset of them (i.e. per-user overrides per-machine, non-PythonCore are excluded). Relying on py.exe being available (it's optional), being in a certain location (there are multiple possibilities), and having parseable output (which is a *big* implicit guarantee) doesn't make me comfortable.