Related: typescript 5.5 will contain type checking improvements. https://www.totaltypescript.com/type-predicate-inference

I agree this is mostly to help in the moment of programming, and most of the information can be thrown away afterwards. The one exception I would make is the reasons why decisions were made, as this is impossible to derive from the code but can be very important for the future when changes need making. You make an important point though - everything else goes out of date but the code never lies.