Yeah, protamines are protamines. If they are not protamines they are something else. Unless you plan on falling on the Something changed into something else a billion and a half years ago. They were quite unlike the protamines and histones of today argument.
Allow me to be the first, apparently, to disabuse you of this notion that you've somehow internalized, that protamines are somehow defined from a list of compounds X, Y, and Z, and things not X, Y, or Z are therefore not protamines. It doesn't work that way, despite how convenient such a definition might be for your purposes here.