There must be intricacies in plastic kit tool engineering the likes of us just don't understand.
Apparently tooling diecast models is much more forgiving, although, going by some of the 1/24 partworks, there also are seemingly irrational things going on, for example a sedan and wagon version of the very same car evidently having different bumper and grille toolings, despite these parts were identical on the real cars. One would wonder why they didn't just reuse this part of the tooling for version 2.
I discussed this with Axel Fischer (of Norev fame) a while back, and he explained to me, assigning a project to a team start to finish is easier than managing the reuse of specific components, especially if the models are manufactured in different facilities, or even different countries.