New Tri Bike Pre fit questions

I have never bought a bike from my local bike store before. I have been looking at local tri bike stores websites to see the kind of tri bikes they sell and I have a question. When you want to shop for a new tri bike, do most bike stores do a pre fit to see what tri bike would be best fit for your measurements? Will they only compare the manufactures they carry to meet your best fit or do they look at all manufacturer tri bike geometies to see which bike would be the best fit for you?

Thanks in advance for your help.