I too asked a former campus rep that I use to do rep'ing with, and he too told me this (He works in management full time now). He said "I believe that if you were to accept the summer program, you would invalidate your Professional Internship applications. If that weren't the case, I think it would still look a bit suspicious." So, yeah, thats two people I have heard this from. I have also read on the PI site that they do get ALOT of applicants for the PI's, and for the one I was looking at they get 400 - 500 applicants a semester. So my guess is they are looking for people that match everything in the requirement section. I think I have decided to take the Summer Program and not try for the PI. Reason being, I found a more descriptive layout of the PI in the internship site, and I dont have good knowledge in a couple of the required tasks, so my guess is they will find someone more fit, and I dont want to lose out not working at all. But thats just me.Good luck on the PI application.
Some pointers that my friend gave me that I would like to share with you if you are still working on applying. "Make sure that you emphasize your Disney experience on your resume. Talk about the highlights of your College Program experience, any extra training you received, any classes you took and your Campus Rep experience (I was a rep). Positive points from here [disney] will serve you well." AGAIN GOOD LUCK!