I had a VW Golf with a DSG (DQ250) which I regularly engine braked on hills. However, I noticed that the instantaneous fuel economy meter would show some consumption on downshifting versus no consumption on coasting in drive.

It turns out that the logic will try to rev match to be in a lower gear before cutting off the fuel again.

Rev matching wasn't perfect either, as going down more than one gear would cause the engine to lazily rev up until it got close enough in speed before the clutches fully engaged.

The DSG offered a Sport mode (obviously to be used when late for work) that would downshift on deceleration, offering a mild form of automated engine braking. I could never quite tell whether would wearout the clutch packs or the brakes faster as it seemed to be a real push-pull scenario between the two.