What safety differences exist between carrying laptops in checked versus carry-on baggage?
It's not about genuine laptops being safer as checked baggage. They're not, they're safer as carry-on baggage, where eventual fires can be identified, isolated and dealt with. That's why we have rules to make passengers carry-on lithium batteries more instead of checking them in. example

The reasoning explaining the ban is that an attacker might use the shell of a laptop to carry something on board. Turning on the laptop doesn't really prove much about it being genuine. You can take a Raspberry Pi that's size of a matchstick box, pair it with 2 AA batteries to create fake internals and  connect them to the original display. That'll make a gutted-out laptop appear to run for few minutes, enough to fool any quick inspection. Leaving rest of space and mass budget to hide something sizeable, like a bomb or a weapon. 

That's why you can't circumvent the ban by removing the battery and taking a charger instead. It refers to "large electronic devices", not necessary ones with a battery.