I am unable to answer, as I have not paid attention to this part of the code base as I have not used
compat_linux(8) myself in at least ten years (for what was then required to build native-mode Java).
I recommend you reach out to Philip Guenther (guenther@) directly, as procfs removal was his recommendation, or ask the group of developers who currently support linux_compat -- guenther@ tedu@, pirofti@, and matthew@. AFAIK, none of these developers participate here.
If you prefer, you could ask this question on misc@. I'm not sure how many people here still use linux_compat. We had one member I'm aware of who used it because he preferred the Opera browser, but he is no longer active, and while he was here he did not have the knowledge or skills to answer technical questions.