Why is Positive being pushed so much by me and others.
It's not because of greenhouse grown, because greenhouse grown also has insects al beit under some control better than open field grown especially re miners.
The method of checking for insects by looking in a glass bowl on a light box was a system that we have finally proven is not reliable at all. Any foodservice that is still using that system, one may not eat any item that requires bedika.
The "complete" positive system of checking including their tollerances, etc is still the ONLY one that is to be relied upon. The OU was the first of the major certifiers that bit the bullet & is instituting their methods by proper training of their mashgichim.
Not all mashgichim are "trainable" to use the positive system. They may still be excellent mashgichim in other areas.
NOTE: The most serious item in hashgocha is proper checking of infestation, and knowing which items require checking. The is no ainoi ben yomo or other kulahs to rely on.