When I was in New Orleans many moons ago some of the criminal court judges would may a big deal out of announcing the bench warrant for no shows during jury selection so the folks that did show up knew there were consequences for those who skip. I don't know how they do it now but suspect you are correct it is done behind the scenes. I doubt they let people skip with no problem, but suspect the enforcement of the bench warrant is lax. Where those types of warrants can bite people in the butt is when they get a speeding ticket and find out they have a warrant too.