These are good points, but this sort of norm is generated by the scientific community anyway. Journals don't enforce ethical norms because it's their job as journals, but because we, as a scientific community decided that ethical standards around human data are important. And journals want to be arbiters of the things that are important.

As with peer review, curation etc - Journals have appropriated this role not because they're best suited to enforcement, but because it props up the edifice that they're important. Establishing community standards, educating trainees in those standards and punishing violations of those standards can (and I think should be) an open process just like the rest of science.