As far as I know, only the hero and the DK can give skill points to a doll. So it would be indeed useless for a doll to invest skill points in summoning doll upgrades.
Don't want to threadjack, but it actually does work. When you are only investing a single point into doll upgrades at the begining it is a minor exploit. If you are going to only put one point into doll upgrades and you have upgrade specials available then put the one point into skills for the doll. Then the doll can use the 3 skill points it receives to give itself 3 upgrades. After the first point you put into skills though you only get 1 pt for 1 pt so there is no further exploit. I don't have a second doll though. If each doll gets 3 + 1 per then at that point there would be a huge exploit with multiple dolls. It doesn't work to put one pt from here and 1 pt from dk though. The game catches this and only adds 1 per 1 if the other character has already added a point.
Sorry again I didn't even address the original posters question. Sounds odd to me though that you don't remember even putting the points in for the upgrades. <img src="/ubbthreads/images/graemlins/smile.gif" alt="" />
