But a 240mm AIO has no advantages over a good air-cooler

Space constrained cases (ITX, mini-ITX) are basically only for AIOs.

Bloomberg noted that Apple also has to be careful not to infringe Qualcomm’s patents, which may be slowing design efforts.

This probably is the slowest and most expensive hurdle to overcome. Qualcomm is a patent giant in this area, its almost impossible not to trip over something they have patented.