That's exactly what is supposed to happen, the default ( or when there's no setting ) it's 1, that is DO the freeze, as GSX always did.
With some planes there's no shaking at all, and it completely solved the bump at the end, but in others (like the PMDG) it doesn't fix the bump and results in the pushback shaking, thats' why we now default to DO the freeze, which means either no setting in the .INI or pushback_freeze = 1, which equals the previous behavior.