That number is just taken from the actual file - on top - in each template. So its up to the creator of themes to adjust it.
If the theme is announced to work with 1.0.2 ,but it says 1.0 in this, then just ignore it. Some creators do update the number, others do not. I think I maybe didn't update that number in some files of Helios, but files IS updated with necessary code changes. And thats what important.
In the default theme its another matter, here it IS tied to the number, because the official default them always has it updated. But as you probably have discovered, some files there too, are 1.0.1 or even 1.0 , and not 1.0.2.
That simply is becuase the files hasn't changed since 1.0.1 for instance, and therefore work and look just the same. When a big change come along..like 1.1 for instance, it will most likely change all the file numbers again.