I've also heard the Estes skill level origin story directly from Dane. It's a quirk of Estes practice since, with a couple of notable exceptions, most other surviving hobby kit manufacturers have only suggested ages, or no rating system at all.
- ROKR no-glue laser wood kits - 6 star levels (!)
- Revell plastic airplanes - 5 levels
- SIG model airplanes - none
- Guillow airplane kits - "age 14+" on everything
- Tamiya plastic kits - none
- Dumas RC boat kits - none (serious stuff)
- RC4WD trucks - none
- Model Shipways - "previous modeling experience helpful" (REALLY serious stuff)
- Quest rockets - none
- HangarOne RC aircraft kits - none
- Campbell Scale Models wood structure kits - none
And I'd say that the highest Estes skill level would barely get you in the door on a Model Shipways kit.