The problem
The two editions of the game describe a model in different coordinate systems with different conventions. Converting between them by hand is unbearable, and converting them nearly correctly is worse than not converting them, because a model that is subtly wrong looks fine in a list and broken in the world.
How I know it is right
The geometry transform is checked byte-exact against a corpus of 1,774 real elements. Not eyeballed, not spot-checked. Every element in, every element out, compared byte for byte.
That is the only standard that means anything for a converter. "It looked right in the ones I opened" is how you ship a tool that quietly corrupts the twenty percent of a pack nobody checks.
The decision that mattered
The whole conversion runs in the browser. Real packs are around 17 MB and several thousand entries, which is well past what a typical serverless upload will take, and the source content is licence-restricted so it must never be uploaded anywhere at all.
Running client-side solved the legal constraint and the size constraint with the same decision, which is usually the sign that it was the right one.