I don’t know in what sense you mean “uncertainty”, but there certainly seems to be widely differing opinions on what pyproject.toml should be for in the first place.
Maybe this is a case where the recently proposed idea of a packaging council would help? With the PEP process, there is an SC or PEP delegate who decides in a way that is based on rough community consensus, but not necessarily full community consensus (there will always be a few people disagreeing). I don’t think “setting the direction for pyproject.toml” is something that can be really embodied in a PEP, so I don’t know how else we could “resolve” broad discussions like Projects that aren't meant to generate a wheel and `pyproject.toml`.