In this article
Edo deplores the secrecy surrounding software implementations of kashida insertion logic, and attempts to 'reverse engineer' the logic. This looks to me less like secrecy on the part of the software developers than simply insufficient research on Edo's part. A Google search for
microsoft kashida justification
leads one directly to this detailed MSDN document on the subject:
I do a lot of work with software developers, and they are compulsive documenters. Sure, not all documentation is for public consumption, but huge amounts of it is.