Since these policies are still new, everyone at the airlines (or in line at security) might not be as up-to-date as you. If an employee ever has a question about your bag (or the rules), you can find the policies of the major US airlines below.
"You can travel with these bags as a carry-on bag. If the bag needs to be checked or valeted you must remove the battery and carry it with you."
From American Airline's policy page as of February 1, 2018.
"Customers checking a smart bag with a removable lithium-ion battery must remove it and take it with them into the cabin. Customers carrying-on a smart bag containing a removable lithium-ion battery must remove it from the designed enclosure prior to boarding the aircraft. This is consistent with Delta's policy today requiring customers to place spare lithium-ion batteries in their carry-on luggage."
"Pack spare batteries in carry-on baggage."
From Delta Airline's official statement and from their policy page as of February 13, 2018.
"Effective July 9, lithium batteries that are installed in any checked or carry-on baggage must be removed by the customer. Once removed, these batteries can be transported on board."
From United Airline's policy page as of July 9, 2018.