If I were in the position to do so, I would not support a HF which does nothing but changing the period to another arbitrary number
That's pretty different from what was proposed, which was changing the number in a fork which is going to happen anyway.
My personal opinion is that the power down period should be shorter and I would support the change, but I also certainly wouldn't support the costs and risks of a hard fork just to make that one change.
Yes, I simplified a bit too much maybe. Of course the HF would also bring SMT. What I don't want is to add this "simple" change to this fork, but (if at all) a seperate HF with a more elaborate concept.