It is possibly a fair estimation...but still only an estimation. Plus how can one break down the figure into those killed by PA directly (innocents and combatants), those by PA allies (how many were inside/outside PA control and thus PA culpability in those), how many died in face of battle, how many through disease etc resulting from combat, how many through mistaken targeting, how many of the deaths were pro-Pakistan forces (both innocent and in combat) etc etc etc...
This is why 3 million figure should not have been used as a smothering blanket, but Nuremberg like trial post-war with solid international arbitration (at least from say USSR, India, Eastern Bloc, France, Romania, Brazil etc given cold war environment) where all information streams are processed as openly as possible (its not going to be 100% perfect of course and kangaroo court veneer will always be there given victors write history etc). Instead both BD and Indian leadership commited this propaganda blunder to get back to status quo and many murderers were let off scott free on both sides....and we will never know any real truth of the scale....and BD govt today quite wrongly still treats this number as unquestionable with liability of prosecution (and no comparable evidence chain like used by countries with holocaust denial statutes in the west+Israel).
I get everyone wanted to move on as quickly as possible, but actually there are these long term problems now in exactly that (moving on) because of the strategy adopted. Committing a bit more thought and finance back then to such would be saving much time, money and relations today (multiplied many times over).