In practice
The value is in where the layers agree and disagree. When customers ask for something and their behavior supports it, you have confirmation. When they ask for it but don't use it, the gap may tell you more than either signal alone.
Compound signal isn't an average of 3 scores. Averaging removes the tension that makes the combined view useful.
Why it matters for product builders
Each layer has a blind spot. Voice favors people who write in. Behavior can't explain motive. Ambient signal is broad. Read together, they check each other.