We had our kitchen floor replaced.

The new floor uses Bruce prefinished oak. The contract said that they'd tear out some plywood under the old floor, else the new one would be too high..

The floor mainly looks OK, but my wife is now really ****ed off because it slopes in a way the old one didn't. Meaning: It's an eat-in kitchen. The eat-in part is in an addition. (There's no wall between the kitchen part and the eat-in part.) Now, roughly at where the addition meets the main footprint of the original house, the floor slopes downwards. A nearby cabinet makes it look like a drop of about 3/4 inch for a couple feet run, at least there.

I suppose there are two ways this could have happened:
(1) The contractor didn't execute the stated plans correctly.
(2) The plans were adhered to, but whoever put the plywood in before did something to even out the slope, and this "balance" was upset when the plywood was ripped out.

My question is: should the contractor have observed this problem and alerted us to it before putting the new flooring in? Meaning, I can see that they shouldn't have to finish the contract without additional money if there was something screwy they couldn't have known about before, but should they have alerted us to the problem and presented alternatives (like, "for $X we can try to deal with that, or you could just ignore it and we'll continue")?

The place was pretty highly rated in our local ratings magazine.