Reddit Dude, because I was forced to dive this:
“Bathtub” is the the nickname for the overall waterproofed underground enclosure formed by slurry walls and foundation slabs. It “holds back” the surrounding groundwater like a bathtub holds water. The last time this was in the zeitgeist was after 9/11 when the WTC bathtub was cleared of debris. I’ve never heard it called reverse bathtub but since it keeps water out instead of in, it is like a bathtub in reverse.
Very on brand for Trump. He hears something from a knowledgeable person and tries to repeat it because he desperately wants people to think he’s smart. He overcompensates and reveals that he barely knows anything about the subject. References: rake your forests, bleach the blood, sunlight the body, water and magnets don’t mix, etc.