You seem to have missed the point. The problem is not too many bench trials; after all defendants may usually choose to have such a trial if they wish. The problem is the vast majority of people in prison because they were intimidated into a plea, not because a jury of their peers convicted them.
I did not miss the point. The article repeatedly noted that trials subject the evidence to more scrutiny than plea deals. A bench trial would have the same effect as a jury trial here. The article asserts that trials are valuable. OK. However, throughout it subtly shifts and says there are few trials by jury and asserts this is a big problem.