You're thinking too complicated in my opinion. If you're crossing a radial to intercept it, you're not established. If you're on the radial and heading in the proper direction, you're established. It's really that simple. However, I've never seen any document specifically stating that so I couldn't give you a reference.
The way airways are designed in the sky is so that you have protection along the sides of the airway as well as turn protection. Look in the IPM for diagrams showing the dimensions of the protection of airways.