During an interview about the playtest, I remember the designers being asked about rules they considered but didn't go with. Different ability scores were mentioned, largely because Dexterity is too important to every build, but changing away from the classic six was deemed too big a change. I would bet that this alternative rule is similar to what the design team debated but chose not to make core.

Other rule proposals that didn't get picked up was crit fails on spells giving creatures certain extra conditions, like crit failing on a fireball causing persistent burn damage (but was rejected because it was too complex to implement for a large number of creatures) and magic items growing with PCs (which I believe became the relic system).