all you say is true, but I'll point out that back in the day it was common to require proprietary compilers to compile things for some environments. The requirement was never to include the compilers, even though it was impossible to recreate the binaries without them.
This point is a fairly major split in the community.
One one hand we have people who say that if they can't compile the exact same binary (and install it), the GPL really hasn't been complied with.
On the other hand we have people like Linus that say that if they get the source code, that's all the the GPL requires.
Now, when you get to the point where there is a legal challenge stating that you have not complied, merely producing source and stating that it's what was used is not likely to be good enough. At that point a company could stand on that point and take it to court, or they could work with people like Bradley to convince them that it really is the source, by providing them with whatever help is needed to let the compile the source to get the same binary. It's _far_ cheaper to do that sort of thing than it is to pay lawyers to go to court.