sentience pops up along the way even though it's never there to begin with

Yes, many events become less probable on higher scales, not vice versa. There is no reason to assume choice should pop up along the way when it's never there to begin with though.

“Your Honor my client pleads ‘Free Will is an illusion.’”

On a macro level, time reversal ain't so easy.

I don't know what experiment you're referring to, but what occurs on a microscopic level does not automatically translate to a macroscopic phenomenon. For example, any particle collision can be time reversed.

Now I'm gonna go commit some crimes and deny responsibility based on the absence of will and choice. My defence is waterproof

It disproves the assumption that the choice of which property of an object to measure in any way can have an effect on the outcome of the measurement, proving it is all predetermined