Well, I wasn’t thinking that so much as that the idiot who wrote this got it reversed. A great thickness of ice will cause the underlying rock to sink, not bulge, because of the weight of the ice. Then, after the ice melts, the rock rises again. It’s called isostatic rebound. Whatever is causing the Washington area to subside, it’s not ice melting.
New York’s Adirondaks are still rebounding after 10,000 years.