What would the college have done if 54 TAs had quit...
It's much easier to fix one missing TA, be redoing the grading work if necessary, than for 54. And if a TA quits, I would expect the TA to release the grades as far as they have been determined at the point of quitting.
1) A TA can get hit by a bus tomorrow. What do you do in that case? You can just do that here.
2) Waterboarding and torture have been demonstrated over and over to be ineffective. That mere idea that they might ever be a useful tool is pernicious and needs to be denounced even when said in jest.