Anyway, Snowden could have made sure to personally review everything he turned over. It's certainly an open question if such a leak could have been as effective, but it would obviously be an improvement in some ways.
And yes, I do think that the person with security clearance minimizing their leak is a better than a reporter doing it.
Isn't that what happened? Snowden didn't give Greenwald access to the NSA network. He chose a subset of the information. Even that subset was more than would be prudent to make public, but filtering it further is a labor intensive process beyond the capacity of one individual, so he chose people he reasoned could be trusted.
It's not like the government would have provided a team of researchers with security clearances to help him sort it out.
Further, argument falls apart when he hands it over to journalists clearly unable to stop nation-state opponents per the very leaks. Of course someone hacked into them or bribed/coerced a copy. It should be assumed even without evidence given what we know.
It's a problem that the internal whistleblowing mechanism isn't working, but contractors shouldn't be picking reporters that then filter national secrets.