Is it true that dub compiles everything in the source dir whether it's imported or not?

[Casper Færgemand" <shorttail at hotmail.com>]

On Saturday, 11 January 2014 at 13:46:51 UTC, Gary Willoughby 
wrote:
> I've seen this but the problem is not with my project but a 
> dependency. I only include two files from the dependency but 
> when my project is compiled the entire source of the dependency 
> is compiled and produces the error.

Is that by any chance also why compiling with Dub is slower than 
just with Dmd? If so, it would be nice to not do for non-release 
builds.