The McDonalds website now (and maybe for awhile now, I never paid attention until this conversation started) specifically states "100% beef". So maybe it was a thing in the past, but I'd still go with DM's comment that it's probabl not very high quality/grade beef. I'm also not sure if you could even have "fillers" of pork or turkey when you specifically state "100% beef".
I cannot speak for the restaurant industry but, at least in the 1990s, in
the packing industry, that would not be allowed. They are supposed to
list what other type of meat my be in the product, as well as if it has
soy. If they are not 100% beef, pork, etc., you cannot label the product
as such.
---
þ BgNet 1.0á12 ÷ moe's tavern * 1-502-875-8938 * moetiki.ddns.net:27