There are dozens of poorly documented EDA project formats and unfortunately they are usually associated with expensive software. And KiCAD has little support for many of them.
For instance I most recently came across OrCAD, yet another EDA tool I have never even heard about it before, it’s proprietary format locking away design information and thus requiring tedious and error prone reconstruction of what is otherwise a completely open design.
I’ll compare it to Blender, where the support for all but the most ludicrously esoteric formats has been developed and in many cases is still maintained. Sometimes even better than the original tools for the formats were. Blender has done an excellent job of supporting otherwise proprietary formats originally developed for and used by software with a median cost in excess of $1000USD (if not that price per year in some cases).
I don’t expect parity, I’m aware of the challenges and appreciate both the complexity and even the difficulty of getting hold of these files in the first place for reverse engineering. However to call KiCAD’s support for EDA file formats in general “excellent” feels disingenuous. It has excellent support for a few of the most popular formats and very patchy support beyond that.