Faster compilation thanks to reduced classpath size?

documentation claims: faster compilation thanks to reduced classpath size.

Is this actually true?

Of course why would you doubt it?
If there are less classes on the class path, there is less to search for if a class is needed for compilation, so the search is faster.
And besides that, if A is not on the compile class path, there is also no recompilation necessary if the version of A is changed.