Digital BW, The Print

I have just created my own grey icc profile using Roy's program. I then 
used this instead of Same as Source in PS, with ABW mode. The result is 
a better print. Excellent !! However I do not really understand why 
this works. Using the grey icc profile in PS and ABW mode means your 
using colour managment in PS and the driver - double profiling. Could 
some kind sole explain how this works.

Many thanks.

Peter.