Another thing that happens a lot is they will either forget to or just not, cut the 1 1/2 tread height off of the bottom of the first riser. Then you end up with the first step being an 1 1/2 taller than the rest of the steps & the top step an 1 1/2 shorter.
In most cases adding floor covering won't make the steps higher because you will be adding floor covering to the floor & each tread so it will remain the same.