I looked on my game shelf and noticed that the offline installer only installs to v1.31533. But the patches claim it's supposed to go to v1.43. The game shelf is missing several patches, so I have no way to fully upgrade the game to v1.43. I've attached a screenshot.

check GOG DB
https://www.gogdb.org/product/2147483111#builds
https://www.gogdb.org/product/2147483111#changelog

latest build is "1.31533" (2022-07-21)
and Patch (1.42 to 1.43) is from, like November '21

Now that is interesting. But why did they change the version format? Wouldn't it make more sense for the latest version to be something like 1.60?

Yes.

I was just about to ask this question. The last installer I downloaded was v1.56 (Feb 2022) but the website says an update available but I see v1.31640 it is just really weird cause to me that sounds like a lower version number.