This.
I am straight and I do not want to put in my mouth or my vagina a cylinder made of arm/leg flesh. Hell, even the idea of touching it makes me freak out. I can only imagine what lesbians and straight men think of a canal made of a penis and/or a rectum when contemplating cunnilingus.
Oh people can tell the difference. I've seen plenty through various sources and they do not look like real vaginas. They really need to stop fooling themselves.