According to my source, most brands of boot and shoe are sized in 1/3" units in the U.S. [e.g., Riedell!], with no well defined origin (varies by brand, by sex, and by the child/adult distinction), but by mm length increments in Europe. Some Canadian brands use 1/3" units, some use mm.
In some cases and for some brands, boot sizes are done by the total length of the foot, but in others it is just the distance from the heel to the ball of the foot, which is considered by many to be the most critical fit parameter for several reasons.
Blades are sized in inches, so it wouldn't really be possible for boot size and blade length to be the same for all sizes. It is actually the length of the mounting plate - typically chosen to be the total length of the boot's outsole or a little less - up to about .25". (I think that sizing makes no sense from an ergonomic or optimal performance perspective, but almost everyone disagrees, and almost everyone does it.)
There is no reason why there should be a one-to-one correspondence between these things, especially given the incredible variety of shoe and boot shapes, and the differences between different brands and genders.
I wear about a men's size 6 or slightly less boots and shoes, and my blades are 9.75 inches. (My boots are custom Klingbeils, but when I wore Riedells, 6 fit best.)
In any event, if you are a Riedell women's size 10, and we assume that is about a Riedell men's size 9 (not sure if I got that exactly right), your boots are about 3 sizes = 1" longer than mine. Your blades are about 1.25" longer than mine - so your sizing is roughly right, since my blades are a little shorter than the boots, and could therefore have been almost .25" longer.
So I think you are just about right!
If your coach wasn't aware of the difference between men and women's sizes, then that would require that your blades be another .75" - 1" longer than they are, if I got the conversion right. So I think you are right to see the men's/women's sizing difference as important.
Hope that helps.
But nothing good would be achieved by telling your coach "I told you so."...