... and that ticket hasn't moved, because fixing it isn't trivial.
What we're doing now — as has been the case for several years, already noted in the previous discussion — has very little end-user value. Also as noted in that thread (as in the ticket)... that's unfortunate, because it did bring some real benefits (and could possibly do even more.)
But, I think it's time to move on. We have ostree and various container-delta approaches. We should focus on those — and give DeltaRPMs a sad, fond farewell.