Have you checked with your local building dept. or Board of contractors to see if they need a state licence or just taking someone else's word for it?
I have to agree with your logic.
Just read the hundreds of post on this and any DIY web site about all the slabs failing, footings cracking or tipping, front porches sinking, Ect.
I see it almost everyday where the concrete guy is poring concrete decks even with the thresholds right up against vinyl or wood siding.
Yesterday I saw one where they pored a walkway and had the slope where it meets the threshold to the garage right under the threshold, against the vinyl siding and as if that was not bad enough it was at a angle running right toward the threshold.