Calls to str() must use the old tp_call protocol instead of tp_vectorcall, as PyUnicode_Type does not implement vectorcall.
All other common types, including list, dict, tuple implement vectorcall. For some reason str got overlooked.

Linked PRs

• gh-117709: Add vectorcall support to str() #117725
• gh-117709: Add vectorcall support for positional-only arguments of str() #117746