This "perpetual fallback" is unique to Rhino. Compare this to Adobe Photoshop, where if you cancel your subscription, the software stops working entirely. With Rhino 7, a valid perpetual licence key means the software is yours.
McNeel provides three distinct methods to manage your Rhino 7 license key. You can choose the method that best fits your workflow during the initial software startup. Method 1: Cloud Zoo (Recommended) Rhino 7 Licence Key
The key is validated online once and stored locally. This "perpetual fallback" is unique to Rhino