Maybe I wasn't clear enough:
the pushback_freeze = 0 is not default, as I've said, and it does work, but it's not as if it would remove the jump on ANY airplane. It worked somehow with the default A320, but it caused a very wobbling pushback, it's still there in case someone would prefer that to the pushback jump but, in general, it shouldn't be used.
There's no way to remove the pusback jump entirely, the jump might be small or big, depending on the airplane and the airport, because it's a result of altitude difference around the apron so, even on a single airport, is not even the same depending on the location.
As discussed in other threads, a possible way to "fix" this, would be using the default pushback method, which would likely make the pushback less accurate, and it's not a quick fix.