I heard Rav Belsky criticize the method of calling up a company or writing to them asking if their product contains xyz, saying that any info a company would give would generally be in a way that won’t cause them any liability and that companies are careful about that, and many times the one responding to the inquiry doesn’t even have full access to the info necessary.
I think he was referring to Rabbi Blumenkrantz’s method, though i’m not 100% sure. I’d apreciate if anyone has more info.