The second half of your last sentence is the only thing that makes any sense... Unless you are trying on a Scarpa, the whole & half size of boot are the same thing. in 99% of the alpine boot world, size 28 and 28.5 share the same shell and the exact same liner. Some companies, like Atomic, put a 2mm shim under the insole of 28.0 to take up a bit of volume or they put in a thicker insole. But other than that, the 28.0 and 28.5 are the exact same thing and it doesn't matter which one you buy.
OP- just so you know, my foot is a 10.5/44.5 and I wear a 26.5 ski boot. There is no correlation between street shoe size and ski boot size because length is only one part of finding the right boot. Volume, width, general shell contours, and liner profile affect the fit. This is why everyone is saying go to a boot-fitter, because this person who can see your foot and examine it IN THE SHELL. Without this, you will be flying blind on the most important part of your gear selection. It sucks that a boot-fitter isn't close to you, but try to make the journey to one. A 2 or 3 hour drive to a good boot-fitter is very common. Worst case scenario, I would trust your coach.
