That they include "rules" and "procedures" indicates those definitions are based around the "what" rather than the "why". A rule of thumb is something passed down, while a principle is something you come to from experience. A rule of thumb likely started as a principle from someone else.
Rules and procedures are a further watering down of the original idea, where even the rule-of-thumb's justification isn't paid attention to or even has been lost over time.
Your definitions are very interesting there mate. In some contexts, yep, what's often called a rule of thumb (for example, sparkies use a multitude of <X>-hand rules[0][1] and call them rule of thumb, because you know, there's a thumb involved) are passed down.
But people are entirely able to derive their own rules of thumbs, if we hark to the common definition that a rule of thumb is a principle/procedure/process derived from practical experience.
For example, I rapidly developed a rule of thumb when dating post-divorce that any person who said "I hate drama" in their dating profile is in actual fact the source of any drama, but it took me a couple of disastrous dating attempts to develop that rule of thumb.
Rules and procedures are a further watering down of the original idea, where even the rule-of-thumb's justification isn't paid attention to or even has been lost over time.