KT120 for Primaluna or Mystere?

Would anyone know why Primaluna and Mystere do not recommend KT120 tubes as Kt88 replacements? Is it because of their auto bias feature?
I would assume it has something to do with the circuitry rather than the auto-bias feature. I would contact the PrimaLuna rep for the US, I believe his name is Kevin Deal. Don't have the contact info in front of me, and I have never needed to contact them before, but I hear he is great to work with, and very good at answering such questions.
did you ever get an answer?  I noted the input/driver tubes  are different and that the transformers may be different as well, but not too sure on that one.  The lesser offering drives EL34s the bigger amp can use a variety of power tubes which you see in Prima Luna as well.

In a Primaluna Dialogue Premium Integrated of recent vintage , the KT120's functioned flawlessly . The sound from this tube however was not to my liking . It did the extremes quite well but the mids were MIA .

Hope this helps .