If there was an open package of meat with a Kosher label, would you buy it there?
To be fair, we are more machmir on d’rabbonons than on d’Oraisa.
http://beta.hebrewbooks.org/tursa.aspx?a=yd_x4376
Still, I think there’s a reasonable enough chashash that it might be switched for financial and/or logistic reasons that it would be a problem.
I don’t think the fear of getting caught in this situation is comparable to the seal required by the Shulchan Aruch.