You are right that that was the common belief, but it was long known that ecosystems are delicate things and carrying out such a campaign without so much as a test run on a smaller portion of the country to observe the impact was irresponsible. It was a case of Mao's genuine faith in the people backfiring due to not always being tempered by the "scientific" part of "scientific socialism".
"Sparrows can fly,"
Yeah, test results would not be 1:1 with a wider-scale implementation, but it surely would have still shown bugs getting out of hand, even if to a lesser extent.