I don't see the security relevance of this as the FMs are not released and only used internally and not RFC-enabled.
You won't find more information than the code in the FMs themselves.
The website linked to above also just automatically extracts the names of FMs and their parameters from SAP and reproduces it on their website - they are not really interested in the FMs either.
Please explain why you are asking this question?
Cheers,
Julius