Ugh, wtf? "The Snow Leopard Installer" didn't do it. The user did it. If you don't expect that an OS reinstall will set the software that it includes to a certain tested baseline that in some cases may be a "downgrade" from certain of your most recent updates... well, that's sad for you, but it's YOUR PROBLEM. You installed it, and you unfortunately have totally unreasonable expectations.
It'd be nice if the Flash plugin were sane like every other internet software in existence and took responsibility for its own security updates, but since it doesn't, your beef is with Adobe. Not Apple.
And every installation of Windows, along with every other OS ever made in history, does this. Sorry to break it to you. It's just a fact of life until someone comes up with something better.