According to the spec:

A build back-end MUST honour statically-specified metadata (which means the metadata did not list the key in dynamic).

In other words, if a field is defined in the [project] section, and not declared as dynamic, the spec suggests it must be used... verbatim? I think? So in theory we could read the metadata directly without executing any PEP 517 hooks.

This would not work for Hatch projects that rely on context formatting: pypa/hatch#1331