Note that this prevents the external tanks from being emptied first, which should still be a very good tradeoff for small tanks (like 2.5t and 10t ones) that need to be used in clusters (or on drone swarms) in order to provide tangible benefits - with multiple tanks it's much harder to lose a lot of delta-V to penetrations even if they are unprotected but there is no longer massive lag and crashes from jettisoning all of them.