> only available to those who you've distributed the modified program to
That's not true. GPLv2 text:
> Accompany it with a written offer, valid for at least three years, to give any third party, for a charge no more than your cost of physically performing source distribution, a complete machine-readable copy of the corresponding source code
There's two issues with that. First, that's only one of three available options (two for commercial entities) that satisfy the license. The other is to include a copy of the source code with the software distribution. However, separately, this does not require that the source code be posted in a public place for anyone to access. You only must give with the distribution a written offer. That offer is valid to anyone, but it doesn't need to be posted in public and the source code does not need to be posted in public.
That's not true. GPLv2 text:
> Accompany it with a written offer, valid for at least three years, to give any third party, for a charge no more than your cost of physically performing source distribution, a complete machine-readable copy of the corresponding source code
(Emphasis mine.)