The wakeup interval is how often the device "wakes up" (from its normal sleepy state, which it does to save batteries--so this generally doesn't apply to mains/USB-powered device) and checks in with Hubitat (or whatever your controller is). This is when it will receive any configuration changes you sent to it. Sensors normally sleep because they don't need to receive anything from the hub (this being an exception), just send things to it. This is unrelated to the fact that the device will send a message to the hub whenever it needs to, e.g., for motion (or lux or whatever)--that just isn't a time when it will do this check.
Some devices solve this by doing tiny wake-ups on a very frequent basis: door locks, blinds/motors, etc. These devices do need to receive messages from the hub on a regular basis. The solution here is "beaming," where they'll just wake up a bit to see if there's anything for them, fully wake up if so, or go back to sleep if not. Most sensor-only devices won't do this, presumably because it's more work to implement for little to no return. (And again, then you also have powered devices like switches/dimmers or smart plugs that don't need to conserve battery and don't sleep in the first place.)
Back to this issue, "possible solutions" is a programming thing: the language compiler/interpreter (for Groovy, which this driver is written in) is just trying to be helpful and suggest method ("function" in other languages) signatures that might match what you're trying to do since whatever was attempted didn't work (in this case, it looks like calling a method that doesn't exist).