The advantage to clipless pedals isn't efficiency. I don't think there's much doubt that pedaling along at a submaximal steady effort, platform pedals work as well as clipless.

But riding a bike, certainly racing a bike, involves more than submaximal steady state efforts.

If you never sprint, never accelerate to close a gap, or catch another rider, never climb a hill as fast as you can, there probably is not a big advantage to using clipless pedals.

There is likely a reason that all racing cyclists, and the vast majority of fast recreational riders use a pedal system that firmly attaches their foot to the pedal.