The only time the "source" of a bonus is necessary, is when you start getting bonus types that do stack. Such as Dodge and some Circumstance and Racial bonuses.
If Untyped, Dodge, Circumstance or Racial bonuses come from the same source, then you cannot stack them. If they come from separate sources, then they can stack except for any special rules each type of bonus designates.
The confusion people are coming across here, is the assumption that ability bonuses are untyped, and so they go directly to the "source" rule.
There is absolutely nothing in the rules that says ability bonuses are untyped. Nothing that even remotely alludes to it.
The fact that there is no comprehensive list of bonus types in the Core Rulebook, any bonus that has a descriptor word before the word "bonus" would be of the type of that descriptor word (i.e. Inherent Bonus, Wisdom Bonus, Dodge Bonus.)
Literally, RAW, does not support, in any way, shape, or form, ability bonuses being untyped.