It isn't. Drag was suggesting different distro vendors could specialise in different areas. If a vendor specialises in a higher-level of the software stack, they will be dependent on those vendors who specialise in lower parts of the stack - marketing disaster.
I wonder can someone acquire sufficient expertise in some area of, say, the kernel fs to be able to quickly *fix* a problem without having or developing an inclination for developing that area. If they can't do that because their employer is focused elsewhere, they may move. I.e. a distro is either going to have to:
a) acquire its own broad-based expertise, replicating the expertise of every other major distro. I'm not sure this is scalable, but even if it is it may be wasteful.
b) work out agreements to get support from every other vendor
c) be at the mercy of those other vendors
Further, I have to say the public ridiculing by one vendor's employees of a another vendor for filing bugs with their *community* bug-tracker left a very bad taste in my mouth. Smacks of all the worst vendor tribalism of the old Unix war days.
If someone can replicate a bug on Fedora why shouldn't they be able to file them with Fedora if that's where the maintainers for that software are most focused on? Why should it matter /who/ files the bug? Shouldn't it be judged on its technical merit, as a record of fact?