it isn't about the battery
The question they are being asked to find out is "is this laptop a functional computer or a possible bomb in which internal components have been replaced with explosives?" Laptops don't have any real empty space or unneeded parts, so if it boots it is probably 100% laptop. This is not completely new, as others have said. Any electronic device is suspect. Pan Am 103, for example.
If a device was so altered triggering it is trivial. So yeah, show me that laptop works, especially if (like me) you have a beard.