Drubin, the disc being played doesn't change the output voltage of the CD player, so the warning remains valid. Reversed RIAA equalization on the Granite Audio disc allows the CD to be listened to after being put through a phono stage. You can actually use any disc for this break in, but you would have to turn your preamp volume to zero for a normal CD.
Having said all that... just play records. If you bought a nice phono stage (I'm assuming you didn't DOWNgrade), it should sound very good to you on the first day, and will improve more with break in.
Cheers.