This is the first thread I've ever seen categorizing it as a jutsu. Everybody else I know calls it a summoning. We could argue about it all day, but no point, I'm still going to believe that it's a summon.No, it's a jutsu. We have no reason to believe otherwise.
Anyway, so why can't Madara use Mokuton:Shinsuusenju?
Not Senpou, just normal.
Even other threads that would ask questions like 'what summoning would you have', people would say Shisuu.