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I don't think that their response is accurate. From their own specifications it say nothing about only dry locations. MC cable is permitted in damp locations. One would also think that if it can be embedded in plaster which can be corrosive when wet it can certainly be in contact with concrete.
The damp location thing is new to the 2023 NEC. In the 2020 and earlier versions standard MC is permitted in dry or damp locations. So the question is under what code cycle was this installed.