Originally Posted by: PlatonicShred
So yeah, a long way of saying that your original thought was correct. Pentatonic scales simply are more ambiguous and the tones you use in them serve to extend the chord, rather than becoming dissonant. ((Just try playing a minor 6th over a major chord--it's over!))

I agree with C Schlegel's post, which points out that this statement is literally the other way around. Being that the scale emphasizes it's determining factor from it's origin and resolves, makes the progression less ambiguous. Ambiguity would leave the progression undefined, or without an obvious definition to the genre. In other words, the sound could be interpreted in ways other than the Blues.
Here's some examples of ambiguous statements.

Walk into a restaurant and the sign reads, "Please wait for Hostess to be seated". A Rather vague way to interpret what the sign actually means.

And another one, "Why did I get a ticket on my car when the sign says",
"Fine to Park Here"?????

More ambiguous tones can be interpreted in more than one way. How you play the progression, leads the Ear to indentifying the statement being made.

Music is a language. We indentify "M" as Major and "m" as minor. In the following statement, "I need to polish the Polish furniture", the minor will resolve to the Major. Vice Versa just wouldn't sound right.
The range of a gifted Vocalist seem to just flow with resolution by accenting their vocal chords with identity.

My Brain hurts...........................