Do you mean the non-product people that designed and wrote typescript?

Exactly, and they did it while no one at Microsoft was looking at them.

That's not what I see from the outside Everytime versioning comes up. My understanding is Microsoft marketing has full control over what constitutes a major / minor version bump like when typescript 4 is released vs typescript 3.9 (just an example). The people who build typescript don't even control their own version numbers.

According to this https://www.learningtypescript.com/articles/why-typescript-d...

The versioning logic is fairly simple (although kind of pointless afaict?). X.1 —> X.9, and instead of going to .10 it simply increments major number. With average releases every 3 months, then major versions are simply being bumped roughly every 30 months.

I think functionally it’s just a really awkward date-versioning on a 30 month calendar instead of 12

It's an old school versioning system that was very popular for DOS software. I'm not surprised that TypeScript, being ultimately still an Anders Hejlsberg project, would adopt it.