There is a similar example for the 777X though. The new folding wingtips to fit into the existing gate sizes seems like a potential new failure mode like moving the 737Max engines forward. No evidence it won’t work fine but it feels like a hack.
https://www.federalregister.gov/documents/2018/05/18/2018-10...
Boeing was required to prove the load-bearing of the hinges on the wings and what types of alerts that the crews receive should a wingtip fail to lock prior to takeoff. More than one means must be available to alert the flight crew that the wingtips are not properly positioned and secured prior to takeoff. If the wingtip is not locked prior to takeoff, the plane is prevented from taking off.
They even required that the electric circuit that unlocks the wingtips be automatically isolated from the circuit that folds and locks the wingtips and that that circuit cannot be re-powered during flight.