We got the "no more than 10 hours" spiel, too. I did an average of 25 hours per week during my P3 year-it didn't hurt my GPA/job offers any. In fact, I feel that my time at work was beneficial in my time management.
Chain pharmacies use intern programs as major sources of recruitment. They can pay you a little more than a CPhT, and get you sucked into their culture. Then, while you're working your 1-2 shifts/week, you take a loan/scholarship from them. By the time job offers come around, they figure:
1. You'll go where you are most comforatble (where you've interned for 4 years, and learned the system)
2. You already owe the a few thousand dollars, so why not get it forgiven by putting in your time repayment?
There is one Wags in the area of my school. No intern is assigned more than 2 shifts/week due to the high numbers of interns there (I think they had 2 techs and 16 interns on roster). All the interns go to Mpls for the summer, and Wags makes allowances for them to stay in the system during the school year by allowing them to all work at this local Wags. The payroll and the hour budgeting are just ignored in the spirit of recruitment.