They used the term Utopian Socialism, not implying that they were Marxist. There are more than two ways. Kropotkin for example was neither.

Kropotkin absolutely was Utopian.

All you're saying is "he wasn't Marxist so he was Utopian" which is wrong as I and the commenter above me already agreed on.

Not at all what I said.

You can even be Marxist and still reject Historical Materialism

You cannot reject Historical Materialism and remain a Marxist, that's a firm rejection of the core of Marxism.