I'm not tiny-handed, more like average, but it's a long reach for my left index finger and not comfortable or intuitive. And no, I'm not a timed shooter most of the time on this rifle, it's a 9mm. Nevertheless I like to drill to reasonable speeds.
At the moment, I'm running an AR180B for .223 shooting and there is no bolt release on that gun, so a moot point.
My next .223 AR build (I've owned many 5.56 AR's, but none right now) is already underway and the lessons learned on the 9mm will translate well to that rile.