Thanks for reporting it. However it definitely isn't as simple as the "harder to kill" issue - it's that the skeets don't see static aircraft as targets and therefore default to general cluster mode. The skeets are meant to auto-home on targets for direct hits. The actual weapons behave differently, not just the effect on tgt.
Now, what I don't know is if real world skeets would ID aircraft. However the dense metal in the engines suggests to me that they would.
I have played the same mission with other units including bunkers, static ZU-23 gun pits etc and all are targeted and destroyed.
We had the same thing with the new Jester LANTIRN - it didn't see static aircraft but that has now been fixed.