Creating amino acids isn't really has difficult as it was thought to be back in the 50's. Amino acids that aren't known on Earth have been found in various meteorites and the like. Although they can be considered bio-markers, they aren't very good ones.

Except that it doesn't. It only shows something about Miller-Urey + 55 years extra reaction time. The experiment needs to be repeated for anything new to be known about it.