I don't think any 1911 conversions allow the slide to lock back on the last round either.
Why are you looking for a dedicated .22 in a 1911 pattern anyway?
On the Old Colt Ace didn't they also have a floating chamber so that the recoil seemed similar to that of a 1911 .45? I have never shot one of the conversions but I am making the assumption they and the new Kimber .45 don't have this feature. I am not sure this would even be a worthwile feature anyhow. I do like any pistol to lock open on the last shot.