Publishing the source like this is risk management for a company. By doing this they don't risk having to receive, vet and process 100's of requests for source at a random time - which could use up their legal department's resources at the wrong moment.
No. They're distributing the binaries, so they have to provide the source code to users of the binaries on request. Publishing it like this satisfies that requirement.
I think you're mixing up the two options that GPL provides. My understanding is that you can either limit your distribution of source to the same parties to which you provide binaries (by "accompanying" the binary with the source), or you can require a request, but you must accept such requests from everyone.
