My mistake; my bleary eyes saw 'minimum' for some reason.
Both the Psion/Wilder have maximum power level just like Wizards/Sorcerers do. Wizards/Psions gain access to higher level spells/powers quicker than Sorcerers/Wilders.
The known powers and when they are learned is supposed to be different, for balancing purposes. The psion has more known powers with less power points when compared to the Wilder, just like the wizard can know more spells but cast less per day when compared with the Sorcerer.
Wizards/Psions = more choices/less castings/quicker learning.
Sorcerer/Wider = less choices/more castings/slower learning.