The moral would be lost though, which I suppose is "true moms, or better moms, prefer to see their kid alive." In fact, if the false mom was genuinely worried for the baby, and the true mom was an Cersei or Lysa obsessive (I will burn cities to the ground, murder my husband rather than be separated from my children, no one can have them!), then the false mom would get the children. You can argue that Solomon's method works to pick the better mother than the true mother, if there is one that's better.

Aside from picking the correct mom, or at least the better mom, if both moms had let go, then Solomon would need to go onto a different line of reasoning to narrow it down (assuming both moms don't happen to be obsessive and rip the kid in two, in which case an innocent baby died to Solomon's first question, oops). I guess the part that people find amazing about Solomon is his ability to resolve an impasse, but if the moms had answered identically "good" in every one of his questions, then he would not be able to pick who the kid would go with. It ultimately seems like a contrived situation, and the solution to even favorable conditions isn't necessarily getting at the actual mother either.