It's stated as much in the initial proposal.
"1) Some contributors are actively blocked from contributing code to LLVM."
> These contributors have been holding back patches for quite some time that they’d like to upstream. Corporate contributors (in particular) often have patents on many different things, and while it is reasonable for them to grant access to patents related to LLVM, the wording in the Developer Policy can be interpreted to imply that unrelated parts of their IP could accidentally be granted to LLVM (through “scope creep”).