Are listed sole lengths of 1/2 sized boot correct?

Yes

Almost all boots (in fact every boot I know of) uses the same shell for there half sizes as full sizes.
That is a if an Edge boot in size 26.0 has a sole length of 305mm, that same boot is size 26.5 will also have a sole length of 305mm because it is the same shell.
1/2 sizes are made up for with thinner liners. As you might guess, the difference in a boot fit from 26.0 to 26.5 will be minimal, the difference between 26.5 and 27.0 will be meaningful. Believe it or not, some boots only differ in the thickness of the insole (by about 1 mm) between a whole and half size. In other words, they are the same size.