The memory-safety-relevant parts of the proposal could be salvaged without keeping contracts more broadly, by saying that the relevant behaviors (like indexing past the end of a std::vector) cause program termination in hardened builds. I'm sure it's more complicated than this but I don't think much more.

More generally, the C++ committee has had a really hard time agreeing on memory-safety stuff because there are a lot of different constituencies with completely different priorities (especially whether they're using it for greenfield vs. legacy vs. something in between), and the incentive is to make proposals sound good to everyone at the expense of actually being coherent.