The calf muscle is mostly used to stabilise the foot/ankle joint. The only reason you need to stabilise them is because the cleat is so far forwards on the shoe.
Move the cleat back and you don’t need to use the calf as much.
The actual loss in usable power for 99% of riding is unmeasreably small. As it comes from the thigh mucsles.
You should also suffer (slightly) less from fatigue, as you will be slightly more efficient (not burning energy just to stabilise a joint.)
I’ve been running cleats as far back as i can for ~10 years. You can feel the difference.
The only downside is a very very slight loss in full bore acceleration at the very very limit of what you can do. But you may gain in absolute peak power.
There’s loads of research, almost all of it shows back is good, forward is bad. Oh, too far forward can give you shin splints and other issues. 😳
Bit like the old pulling up on the pedal myth, good science debunks it pretty thoroughly.