If it is covered with a food-grade (Keyword; FOOD-GRADE) sealant, that is durable, does not flake off, is easily cleanable, and most important that it is approved by your inspector and zoning. (agreeing with Tom on this) You should be okay.
My biggest concerns would be the durability of that surface, and it developing fissures in it, or pieces chipping off through normal usage and cleaning procedures.
If that surface is not acceptable by your health department, maybe consider getting a slab of polished granite to work on that can be inlaid, or placed on top of that concrete surface for stretching.
We have granite countertops here, they are almost magical for stretching dough, and very very durable. My monkeys have not chipped them yet, although they have broken off a few corners on the upright backsplash.
Bare hardwoods also have a great reputation as being very sanitary, but I would not want to try to stretch dough on a surface that is not slippery and that can also absorb water.
Once you seal hardwoods, bacteria can propagate rapidly like they do on plastics and other cutting board materials commonly in use whereas hardwoods tend to kill most harmful bacteria that come in contact with it.
(I can cite a University study to back up my hardwood claims if so requested)
