Unless things have changed (and
@DeltaDogs can correct me since he is far less removed from Swab Summer then I am), you are issued the boots but you don't wear them right away. Even when you do start to wear them, it's for designated periods of time that get longer as Swab Summer goes on. For example, I remember our first time officially wearing them was just to evening formation and dinner. Towards the end of the summer, we were wearing them all evening until showers/lights out. The idea is to help you break them in without destroying your feet by making you wear them non-stop from day one.
Interesting about the two pairs of athletic shoes - we were only required to bring one, and they did the job the entire summer.
@DeltaDogs were you guys issued "go-fasts?" For everyone else, go-fasts is the term used for issued black sneakers that you wear with your uniform during most of swab summer (and then immediately trash the moment Swab Summer ends because the smell is horrific). They're called go-fasts because you're pretty much running everywhere anytime you're wearing them.
Again, unless the rules have changed, I highly recommend buying another pair of boots after Swab Summer. The ones they issue you are heavy on your feet, and are made for actually working - not marching to class. I bought a pair of Nike boots that last me all four years and were lightweight, you don't recognize the difference until you try them on the first time. BUT save the original boots, because they are composite-toe and those are required onboard Coast Guard cutters and at small boat stations for safety reasons.