I’m glad you know them so well. In what way is such a popularly used rule not a rule?

Incidentally I find it interesting that d&d 3.5 specifically calls out that a 20 isn’t automatic success, and a 1 is not an automatic failure, where 5e removes that clarification, simply saying “if the roll plus bonuses is less than the DC the check fails”.

That looks to me like they are leaving it more open to the common house rule