Wow, someone at Apple is really serious about this hobby modding thing.
I think we all accept that it is reasonable to require the extra functionality that Bluetooth 4.0 bring to the table over 2.1 + EDR for the new features in Yosemite (10.10).
The KEXT change in DP3, however, is certainly not customer friendly and feels underhanded to me as Apple clearly only need to check for the hardware features being available and should not be hard coding acceptable logic board ids in to the driver to lock upgraded devices out.
They surely must know that some of their users with the 2011 MBP models will have something like a Computer Science or Software Engineering background, or just experience, and can pick these locks within the binaries, certainly expose them. It seems misguided, in my opinion. The users who make or want to make this change are likely tech savvy, relatively few in number, and perfectly capable of researching the issue to know that they need to use a modified KEXT.
Apple did not lock devices out that were upgraded with a newer wireless card to support AirDrop, why do this now for these features?