Different thing. The false vacuum hypothesis says that there's a base level of vacuum energy, but getting there costs energy to surmount some barrier, which means the universe is sitting somewhere above "true" vacuum energy. If true vacuum energy is achieved anywhere, then it will propagate out at the speed of light and drop everything at its interface into the new vacuum while using the released energy to continue propagating. Basically an unstoppable firewall moving at the speed of light, irreversibly replacing the universe behind it with an unrecognizable new one.
The vacuum catastrophe is a difference between what theory predicts the vacuum energy level should be and what we measure it to be. Theory says it should be so dummy high that the universe is unable to expand, and we observe its expansion accelerating, so the energy must be basically zero.
Different thing. The false vacuum hypothesis says that there's a base level of vacuum energy, but getting there costs energy to surmount some barrier, which means the universe is sitting somewhere above "true" vacuum energy. If true vacuum energy is achieved anywhere, then it will propagate out at the speed of light and drop everything at its interface into the new vacuum while using the released energy to continue propagating. Basically an unstoppable firewall moving at the speed of light, irreversibly replacing the universe behind it with an unrecognizable new one.
The vacuum catastrophe is a difference between what theory predicts the vacuum energy level should be and what we measure it to be. Theory says it should be so dummy high that the universe is unable to expand, and we observe its expansion accelerating, so the energy must be basically zero.