I like that system. I recently took the TripleByte technical quiz and I liked that "I Don't Know" was an acceptable answer for most of the questions. When paired with the timer (or in your case, looking for a fast answer) it seems like a system that encourages honesty and "moving along" so you don't waste time on questions that you will probably do poorly on anyway.
As an aside, does anyone happen to know what the "levels" of performance on the TripleByte technical quiz are? When I took it (and I realize this will sound like a humblebrag), I was told I did "exceptionally well" and could be paired with "approximately 27 top tech companies", but I didn't feel I did all that well on it at all.
I ask because they say they only invite the "top few percent" of quiz takers to continue, but all I typically see when I search this online is other people mentioning they also did "exceptionally well." Anyone have feedback on the process?