Well, it's not obvious to me, even if that's true. You will probably receive it twice (once to discover you don't want it, then once again when it's in a block anyway?) but you won't send it (except maybe with the block again?). I don't know the details of tx and block relay. And I'm not sure what fraction of txs these filters apply to, either.
This is why I was interested in the claim of empirical results, but maybe nobody has actually measured, which is sad.
