On the older Shadows, the fuel cut-off relay gets a signal from the ignition system. If the engine is running after tipping over, the fuel pump will still run. If the engine stops, the fuel pump will stop even when the key is still on. With the relay bypassed, the pump will run until the key is turned off.
Many newer bikes have a tip over switch in one form or another. Harley has a “Bank Angle Sensor” that shuts off the ignition if the bike leans more than 45 degrees to either side. On fuel injected models, it shuts off the fuel pump also. It’s tied into the Turn Signal Security Module.
I watched a guy tip over a large touring bike, Kawasaki maybe. It would not restart until someone told him to turn off the key for five seconds. That’s the same way the Harleys must be reset.