You are assuming that designers would be overly simplistic about their work. Planes don't use their wings for propulsion, so why would a designer try to make them flap? That action isn't solving the same problem, and any engineer would know that. Likewise, tires roll in response to propulsion, whereas galloping legs are providing power. Frankly, the pistons inside an engine ARE closer to a gallop than to a roll. (Well, maybe not in a Wankel rotary engine, but...)

You seem to misunderstand what biomimicry even is. It’s about identifying root problems and seeing how nature has already solved the same problems we’re trying to solve. The whole concept of first principles is there. Remember when Speedo invented new swimsuits that led to swimmers breaking world records left and right? That was due to biomimicry. Because sharks are fast and shark skin is not smooth under the microscope but instead has lots of tiny protrusions that create micro-turbulence along the surface that leads to less overall drag. And then creating a similar material for swimsuits. That is biomimicry. Not making freaking airplane wings flap to achieve lift. But instead, discovering that the way a hummingbird sweeps it’s wings back and forth creates an area of lower pressure above the wing that virtually sucks the wing up. Interestingly enough airplane wings are shaped in such a way that the wind travels faster above the wing than below the wing, creating a similar pressure difference and achieving lift.

The human brain is the best pattern matcher in existence and we continue to learn from it. Think about that.

I think they enter the water with a closed mouth and then open it to grab the fish. I see them frequently when I’m kayaking but they are too fast for me to tell which way their mouths are for sure.