Apple has released detailed APFS specs. It’s almost 200 pages, I’ve only read some of it.
But I’m not sure if it goes into enough detail for Alsoft to write a reliable repair tool. The part I’ve read so far has lots of very low level detail, without a broad overview of how it all fits together. But perhaps I just haven’t got to that part yet.
HFS and HFS+ were in use for decades, had detailed specs, and Apple engineers would answer questions at WWDC or online. APFS seems much more secretive, and Apple is a more secretive company now.