Earlier quoted context omitted.
And this is why focusing exclusively on Boeing in the 737 MAX controversy is, IMO, quite short-sighted. It's not just Boeing's greed. Pretty much the entire industry has been happy to look the other way and enable their nonsense for years, since it meant they wouldn't need to invest extra in training their pilots.
Maybe the discussion should be about how much changes regulation should allow being done to a plane, before it must become a new type. The 737 Max is like double the size of the original 737 - roughly twice the passenger seats, more than twice the weight, roughly 1.5 times the length... How much larger can a plane get, while still keeping the same certification?
Also it's entirely normal for a variant of a vehicle to have significant physical dimension differences. They're considered variants because their [chassis, airframes, hulls, etc] follow the same design and assembly, and because they handle in a similar way; they don't need to basically the same vehicle in a different coat of paint.
I guess a somewhat decent comparison is...Apple makes a type of computer (the MacBook Pro) and releases different variants (and within that, versions) of it. A fully specced out 2023 16-inch MacBook Pro and its entry-level 13-inch variant are both fundamentally the same type of computer even though the former is significantly bigger and beefier. Now, if Apple tried to shove a whole RTX 4090 graphics card into a MacBook Pro's characteristic svelte and relatively vent-less chassis we would say "no, that's stupid. Make a different type of computer if you want to do that". But that doesn't and shouldn't mean that a 16-inch laptop is a different type of laptop from a 13-inch one.
(As an aside, your numbers are a bit off, probably because you're comparing the wrong things. The "original 737" is two planes/variants, not one, and the "737 MAX" is similarly four planes not one)