make repeated goals repeatedly?

[David Boyce]

I'm looking for clarification on what _should_ happen when you 
specify the same target(s) repeatedly on the command line. 
Background: while working on speeding up a particular build I've 
gotten in the habit of running something like:

    % time make -s clean all

The 'clean all' guarantees a complete "round trip" leaving the build 
area in the same state each time. But recently, for a reason which 
doesn't matter here, I thought I'd make it build twice in a row with:

    % time make -s clean all clean all

But what happens is that the repeated "goal" arguments are uniqified 
such that this behaves just like the original. Is this intended 
behavior? I spent a few minutes with the spec (SUS) and it says 
nothing very precise. The GNU make 3.81 manual says in section 9.2:

> If you specify several goals, make processes each of them in turn, 
> in the order you name them.

Which could be taken to imply the behavior (clean twice, build twice) 
I expected. This is not a huge problem - I'm just wondering if 
there's history or a spec in back of it.

Thanks,
David B