No, I think it came with the latest official ROM. I just got my tab the other day, brand new. The firmware on it is XXKG8. I haven't added anything, and as I said, it's new.
I get that message before download mode. I have been actually hesitating to root it because of this, thinking that they have added some sort of counter like on the SGS2.
So this is not the result of adding a rom, it appears on brand new retail tabs as well, it seems.
So from what I gather, nothing happens when you press the yes button to go into download mode after you see that message?