The policy here is re: Kashrut "Kol d'efshar levarurei - m'varinan"
IOW we verify as much as possible and rely upon Rov and Hazaqah only as a fallback position.
RRW: See Rema YD 1 "Kol d'efshar levarurei m'varinan"
R Akiva Miller:
«Whatever we *can* clarify, we *do* clarify. (That Rema is not talking about food ingredients, but about who is qualified to be a shochet. Still, it's a great sound bite.)»
It's more than a sound-bite if Posqim consider this a fundamental principle in issur v'heter.
Especially if they are applying it as an "unconscious" axiom.
"Et hatai ani mazkir"
I always pooh-poohed learning Hilchot Sh'chitah as a [relative] waste of time for most rabbinical students. [Especially when NOT learning Hilchot Treifot with it.]
Many rabbanim insisted that Hilchot Sh'chitah teaches the student fundamental elements of p'saq
B"H I have become enlightened [the hard way] and I see that a number of POLICIES are embedded in Hilchot Sh'chita.
EG Talmudic Halachah requires no "S'micha" or "Qabbalah" for Sh'chitah, but Ashkenazic practice DOES!
It is simple to see how that gets extended to formal hashgachah for many areas of Kashrut. This is especially true today - when chemicals have made the industry highly sophisticated.