The Lich system was pretty close to the mark. Possible that developers gave the underlying features of SoM a wide berth out of caution, but so much of this seems to boil down to "we don't want to risk the possibility of a lawsuit" rather than "we can't just do our thing and see if WB's lawyers care enough".

So long as you're not directly ripping off the code from another system, patent courts have been pretty generous in interpreting overlapping abstract concepts.

But any kind of suit is scary, particularly for studios that aren't geared up to fight them.