I'm in act 2 and have been putting some skill points into summoning doll upgrades to its level and skill points.

I just got the second doll (demon), and it does not seem to have the level/skill point upgrades.

I had thought that all dolls would benefit from the summoning doll upgrades, but it seems not the case. How does it work? It seems lousy that points I invested early are now no longer available to improve this new doll (or future dolls).