The thing is, the people who were saying that were wrong even at the time. Fertility was already declining in the late 60s when The Population Bomb was released, but population was still increasing from the earlier boom, in the same way your car will continue coasting up the hill for a little while even after you release the accelerator. People were freaking out about absolute numbers, instead of extrapolating trends for the data they already had, because they were being actively misled by folks like Ehrlich.

So this is less "we believed one wrong thing, are we now believing a second wrong thing?" than "we believed one wrong thing, and corrected it to what we should have known all along".