You make conclusions based on data which may not be true, so it is hard to say.
NTSB has a public docket with large amount of reading material on website, perhaps some answers can be found there.
I heard the tape where FO says "starting APU", but was the (auto)start sequence completed before the impact at all?
The A320 with dual engine failure (full, unlike Hudson) and emergency electric only retains Alternate law FCS mode. To pilot, this is identical to Normal law except the FBW protections are removed.
Hydraulic pressure on a flamed out engine is available down to about 220 kt IAS, again, Hudson was landing significantly slower than that but any thrust on at least one side should keep both engine driven hyd systems available (via PTU).
Yours,
FD (the un-real)