requiring them in checked luggage is not only for detection but also isolation (containment)
Containment from what?
If they go boom as baggage the damage is variable as hell based on location.
If they go boom in the cabin the damage is predictable based on seat location and/or overhead storage which is specific by PNR (boarding pass).
And then there is the fire hazard from a typical LI cheap battery in passenger luggage. In the overhead or cabin it's specific in location and ability to assess and contain. In the baggage hold it's the stuff that causes extreme workload on the flight crew's decisions vs time and distance to an airport.
I'll leave it to the airline safety guys to sort out the pro and cons and costs vs risk avoidance.