Unfortunately not. The systems are only equal if you shoot exactly the score every time, the bigger the variation in your scores the further above a USGA handicap a CONGU one is.
Take our theoretical golfer at scratch and run those scores again and under the USGA system he stays the same. Under CONGU he goes up 0.1 for every score over 73 and doesn't go down for the 72s (he's already scratch. Over time scoring like this he's back up to 1.5 ish under CONGU but under USGA he remains at scratch.
Yes, but a scratch golfer would most likely have a pretty low variation from score to score. It's not like me where I score (on 9 holes) about 47,48,42,47,43,42, 57, etc. This is why I am a bogey golfer.