Airburst shells were rejected by Relic on the basis of not wanting to alter the role of the unit. So, we're stuck with the bare minimum changes.
On the other hand, Elefant TWP is a lot more useful now. So, that's something that the Elefant does better than the Jagdtiger now.
which is good, because the idea of airburst shells on a direct-fire weapon system, especially a tank destroyer, is ridiculous. they didn't exist in ww2 and they still don't today (the XM29 or whatever the hell it was being the one exception).