Sure, I don't see how that would compare to riding with flats and flat shoes. Of course using tennis shoes to ride the slippery back of a clipless pedal is going to be uncomfortable.

You mentioned you forgot your road shoes at home - never ever doing that is one of the things I like about riding flats. No 2nd pair of shoes to forget. No need to change shoes at the ride. Etc. Less hassle. Less to go wrong.

I think the text I quoted you with might have written that backwards of how you meant it. Seems like you meant to write that you're using less muscles with clipless with with a great deal more output.

Studies and casual experiments have demonstrated that clipless does not make you faster, at least on a stationary bike or on flat ground. The "great deal less output" is just not true. Whether clipless provides a small advantage that becomes important in road racing is debatable.

The question is whether you want to trade a possible small advantage with clipless for the additional hassle of the system. I bike to work and for enjoyment so to me it's not worth it at all. After years of suffering through using clipless because I believed in the claims I had read, I now think people should be able to make their own decision without the tall tales of fictional clipless advantages I've since realized are not true.