Tales of the Bulb
That one has been floating around for years. If the bulbs work, they work...that's it. The cruise control ECU gets a ground signal through the bulb filaments. The bulb tale used to be even more elaborate claiming that the incorrect bulbs would "fry" the cruise box. I only use OEM Osram bulbs. But it's because I LIKE them...no other reason.
Typical ECU failure is a system that will work in the accelerate mode but doesn't hold. Or one that drops out of cruise frequently. I have repaired a few by re-soldering connections on the circuit board that looked different from the others.