Do you really think they wouldn't have bothered searching for AF, or indeed MH if they had the black box data already? Try telling that to the relatives of the deceased...
You are missing the point, they would have known WHERE TO SEARCH.
On the contrary, I was proposing that instead of spending a lot of money on SAT bandwidth and onboard equipment for live FDR/CVR transmission, that money (or less) would be better spent mandating frequent ADS-C via SATCOM on all aircraft.
Then they would know WHERE TO SEARCH.
It would also improve ATC efficiency, reduce airspace congestion, improve day-to-day safety, a whole host of tangible benefits.