The back was likely lifted from E101, which was indeed 50 cards.
I don't think anyone knows for sure why Dockman cut 10 cards, but the theory floated on the caramel-cards website is that part of it had to do with where the candy companies were located. Six of the ten cards cut by Dockman were Philly players. While Crofts (from Philly) wanted those players in the set, Dockman (from Baltimore) cut them. But it does not explain why Cobb and others were cut too:
http://www.caramel-cards.com/e92.html
Cheers,
Blair