And yet, both WINE and ReactOS have refused to use the leaks; ReactOS doesn't even allow people who have worked legitimately at MS in the past to be developers, simply because even the smell of contamination would expose the projects to enormous legal risks.
The only way I could imagine these leaks being useful is by "parallel construction" aka by comparing the source code with actual Windows binaries and then the WINE/ReactOS code to spot out differences to check, and then have a second person investigate the differences with only the note "check function XYZ with implementation in current Windows binary". But that's a lot of effort for very low reward, not to mention you'd need at least two very skilled experts and the low-hanging fruits having been picked already long ago.
[1] https://borncity.com/win/2020/10/01/entwickler-compiliert-wi...
[0] https://www.theverge.com/2022/2/21/22944335/us-copyright-off...