The change was made by GM to change to pull to open, rather than push to open. I am guessing that it was a safety measure, It would be relatively easy to accidentally push the handle forward with a wayward knee, causing the door to fly open.
There is no reason why an earlier push-to-open door can't be converted by installing the later pull-to-open mechanism. The doors are all the same in terms of attaching either one.
Maybe the reason that the push-to-open mechanisms are not available from the aftermarket is because they are a bad idea in regards to safety.
Carl
