Wet Drywall Question
They are wrong. Drywall is gypsum and paper. In the presence of standing water, paper will grow mold and gypsum will turn to mush. It is water-soluble. That means it will dissolve. Give it a kick with your shoe on. It will probably feel soft and mushy.

Replace everything with materials that are not affected by water: cinderblocks, cementboard, lime plaster, tile, etc. Wood and drywall in a basement are, in my opinion, terrible ideas. Basements flood. It's just a fact of life. And when they do, all the pretty wood and nice drywalled stud walls are toast.