It wouldn't cover anything from OpenBSD, if as excerpted by you, it only covers exceptions related to GPLv2 as I don't believe OpenBSD considers GPLv2 to be acceptable either.
My reading of the LLVM Exceptions statement is that if a judge understands the the Apache 2.0 patent provision section (and others) to not be the same as GPLv2, then the section is waived. The preamble of the GPLv2 summarizes its stance on patents in lay terms that seem to be compatible with what OpenBSD wants:
"We wish to avoid the danger that redistributors of a free program will individually obtain patent licenses, in effect making the program proprietary. To prevent this, we have made it clear that any patent must be licensed for everyone's free use or not licensed at all."
The exemption you quoted very specifically says it applies "if you combine or link compiled forms of this Software with software that is licensed under the GPLv2 ("Combined Software") and if a court of competent jurisdiction determines that the patent provision […] conflicts with the conditions of the GPLv2" (emphasis mine). I don't know how you could read that as applying to situations where nothing is licensed under the GPLv2.
In other words, it sounds like this would address OpenBSD's concerns if OpenBSD were GPL-licensed — but it isn't.
