…the liability split should put an end to the stupid conversations that Amphastar will settle with the proceeds only benefiting Momenta.
No one made any such assertion.
What you’re missing is that NVS benefits implicitly from a settlement in which Amphastar is allowed to launch on a future date by dint of NVS’ paying MNTA a much smaller proportion of the collaboration’s profits following such a launch. This means that MNTA can take most (or all) of the explicit transfer payments in a settlement—i.e. a royalty on Amphastar’s sales—while the overall net present value (NPV) of the settlement is split roughly evenly between NVS and MNTA.