Microsoft has a separate backwards compatibility team working on this. Just because they're improving BC support doesn't mean other people aren't working on other things. People at Sony who are building PS VR2 or making new games wouldn't have anything to do with backwards compatibility in the first place.

MS code is completely different than sony's.

That doesn't make any sense. Do you think that game developers develop several different versions of their games for each platform, each with completely different codebase? No.

To assume modding it without touching the code to get it to work is just wrong.

It's pretty obvious that you don't really know what you're talking about. I guess you read about those BC modes somewhere and made a whole lot of assumptions.