You are completely right - and I must give you credit - you're the first theist I've seen that's hopped on the site and actually gotten, without prompting, the point of the WWGHA question. I wish I were kidding, but usually it takes a few weeks of explanation for it to sink in.
All in all, though, it's just a good question. Why are all miracles attributed to God ambiguous? And it's just one question of many - as I read your posts, your answer seems to be 'because God requires mystery'.
My question for you is "where does it say that?" It's a nice thought, but after being Christian most of my life, I can't remember a single place in scripture where it ever says that. It does that that those who can believe without proof are truly blessed, and it does say that testing God is a bad thing... but it also says that even one person with the tiniest shred of faith can work astounding miracles akin to throwing mountains into the sea.
Let's make the question a bit more neutral: L. Ron Hubbard wrote that people who achieved the level of "Clear" in Scientology would have astounding psychic powers: perfect communication, perfect health, the ability to heal others at a touch, even psychokinesis. To date, not a single "Clear" has ever demonstrated these abilities. Shouldn't this make me skeptical of Scientology's premise?
To the same end, not a single Christian, Muslim, Mormon, Zoroastrianist, Savior, Healer, or Saint has demonstrated a single unambiguous act that would equate to the mountain being tossed in the ocean, as promised by the bible. Shouldn't I be skeptical of Christianity due to that fact? If its followers claim miracles regularly, shouldn't even one be able to be shown to be ... well.. an actual miracle?