Villain could interpret your turn bet as;

a)a bluff
b)a made hand which your leaving room to get away fromon the river
c)a made hand which your committed to

Your turn & river combo means
(a) is still possible
(b) kinda ruled out
(c) opponent may be doubtful(see below)

Do you think villain folds AK/AA if you lead the turn for ~ 300K?
Obviously the answer is no,or you would have bet this on the turn, but this leaves your turn & river combo looking a little suspicious.

With the hands you are meant to be value betting this river with (I suppose KK/6x) you would love AA/AK to be facing 16:5 rather than 15:6.

I don’t know your opponent, but a good player might see that your turn bet was engineering the betting so that if you are called you could still fold out AK on the river.
I guess this line of thinking hinges on whether your opponent thinks that you would have thought a 300K bet could fold out AA/AK, but I think most wouldn’t expect these hands to fold for that amount.

Then again I could be just talking *%$!.