Undisclosed patents? That's quite an oxymoron. "patent" literally means out in the open. There are no undisclosed patents here. Even patent applications are public.
It should be perfectly clear from context that I am referring to specific patents that are used as a threat against competitors, without the specific patent numbers being revealed. No amount of searching the patent database will tell you conclusively which patents those are.
Aren't they being revealed to the competitors that are being approached for licensing? Are you implying that, for example, Acer doesn't know which patents it bought a license to?
Also, this list is essentially the top ~300 patents that MS thinks Android infringes on. There's absolutely no guarantee that other patents don't apply now or in the future so the utility of the list is kind of low.