CRNA schools' pre-requisites

I have noticed that different CRNA programs require different prerequisites. For example, some want you to have had physics, then some do not. Some programs want you to have taken general chemistry and others don't.
My question is, that if all CRNA's take the same board exams to become licensed, why are the pre-reqs in different programs so different?
I've heard someone on this forum say that if you're accepted into a program they will teach you all you need to know. Is this true?
What if, for example, someone decides to take general chem and physics (while working in ICU of course ) and is accepted into a CRNA program that has not listed these classes as requirements. Does this person have "one up" on the other students that have not had these 2 classes? Is this person more prepared for the chem and physics courses actually taught in the CRNA program because of previous exposure? Or have they simply wasted their time and money on the extra courses?
And vice versa- with nurses applying to 20 to 30 CRNA programs because of the competitive nature of the application process, how will they ever complete all of the pre-reqs that ALL of the programs require (since each program requires different things)?
Please help me understand.