Interesting, wasn't aware of it. All I remember there was an interview where he was asked about Swedish extreme metal like Opeth and Meshuggah, and he said something like technical metal doesn't fascinate him because he can figure out the rhythm quite easily, and said nothing about Opeth altogether. I've always understood it as basically "meh", but then I guess I misunderstood it. Mikael on the other hand was asked about them in Metal Hammer here and he just said they asked PoS once to tour with them.