This has been remarked on in another thread. Unfortunately manual editing is still necessary.
I would say that the hierarchical sheet concept is not fully evolved. There are many situations where could work better. Parameters as you have pointed out is one aspect. So the format is also a work-in-progress and shouldn’t be regarded as definitive. Probably by KiCad v12, it will be totally unrecognisable compared to now. But how to get there and what the UI will look like, well that remains to be seen.
Just adding that I’m not a dev, so these are just my opinions.
Edit: Just want to add that I think it’s really the code you should look at, not the data format. If you think of the schematic format as a language, then the language generally allows you to express things that are nonsense, which is true in both human and computer languages. The semantics expressed in the program constrain what is actually generated.