I don't think Lionel is trying to save money by only using 1 screw, I think it's just the typical quality control we are forced to live with.
Thanks to the OP for posting this. I have a few engines that may fall into this even though they are not LionChief.
One question, can older PE units accept the new motor? I am thinking if Lionel thought to use a more expensive part in the newer ones, I should upgrade while parts are available if I can... I also have a PRR Horseshoe curve set with the Berkshire.
Tony