I have never heard of this! I don't believe him. Did he give you a botanical name for this special plant?

Why plant a flowering dogwood that does not flower? More likely these are seed-raised plants that will not flower as small as grafted stock.

Yes, perhaps what he meant was it was "NOT" flowering dogwood which is the common name for this particular dogwood:

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All other dogwoods DO flower, they just have a completely different looking flower, like this for example:

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There are other bracted dogwoods besides Cornus florida, for example the also very popular C. kousa.

All angiosperms (non-cone bearing plants) flower - even male varieties and sterile hybrids - that is how nature intends for them to reproduce. The flowers may require a specific age before they are produced or they may be so inconspicuous as to appear not to be present but it's gonna happen sooner or later. Even if the flowering parts do not work as nature intended, they will still be produced unless manually removed or prevented from forming.

Being an old landscaper myself, I would say the most likely scenario is that your landscaper is either incompetent or unethical. Or they could be saying exactly what the builder told them to say. Non-flowering my hiney.

Dan

Can you post a picture of the plant. Fifteen on one side of a house makes me wonder if it is a small shrubby dogwood species.....or a very large house.

I completely agree with Dan. I'm an old landscaper myself.
There is no such thing as a nonflowering Dogwood. If there was, who would want it?