I think that flight path of the a/c with HS in full down position (as claimed on RU tv) should be different. Definitely not a straight line - like we can observe in video showing last few seconds before impact.
But this scenario maybe coul'd fit when to presume that pilot counteracted with full column pull back.
On the other hand, to move stabilizer to full down position (f.e. with elec. stab trim) you need time - it's 30 maybe 40 wheel turns from nose up position. And on the presented ADS-B data we can see rather fast pitch drop (from +10 to -30 in 7 sec.)
So something still is very unclear in this case