I understand the article's emphasis on exercising good judgment around release timing, but read-only Fridays are not there for the people who generally exercise good judgment. If you are the sort of person/team that is likely to deploy late on a Friday afternoon despite the inherent risk, you are likely the kind of person/team who underestimates or ignores risks in general. This includes the risk of a given deployment, thus exacerbating the impact of your late-Friday deployments. It is therefore sensible to simply take the decision out of your hands.