Is the 33" the interior or the exterior dimensions of the sink? A 33" sink usually means that the interior dimensions are less than the 33".

A sink base (or any cabinet) is measured from end to end. For example, the total length of a 33" sink base is 33". Depending on the type of cabinet (frameless or framed) and the thickness of the sides, your interior dimensions will be reduced.

For example, my cabinets will have 5/8 inch thick sides so I lose 1 1/4 inches in width from my cabinet. So my 33" base can accommodate a 31 3/4 inch width sink.

Since you are having your cabinets made, I would give a copy of the sink specs and the installation instructions to the cabinet maker so he can then tell your KD the size of the sink base you will need for your sink.