Itche:
I don’t know what this practice entails, and I don’t own several old siddurim.
I only know that Weiss and his kookoos are not motivated by a desire to reinstate old minhagim, but by a desire to make Judaism fit into their notions of morality and values. And that is treifer than chazir. (Because it doesn’t even have split hooves.*)
*Actually, chazir is more treif than other meat, specifically because it has split hooves. I forgot where I saw this (I think a rishon on the page), that being closer to tahor actually makes it more tamei.
Perhaps we can say they are exactly like chazir, since they hold up their “split hooves” in the form of old siddurim or the Rambam or other sources, and try to pretend that they are motivated by proper hashkafa.