Maybe you could expand on this statement a bit for us?
In order for the ABS to modulate the brake system to prevent wheel lockup, it is tied into the fluid section of the braking system and the leaks could come from various places in the system where ever there is a connection.
I am sure we all understand the fundamemtal principle of ABS, namely that it detects rapid changes in wheel speed (i.e. lock up) and modulates pressure to ensure brake torque is maintained just short of lock up which is why the pulsing sensation is experienced.
Clearly do this there is a modulating pressure control valve in the brake line, so perhaps my statement above wasn't entirely clear. What I mean by that statement is that the ABS system has no capacity to absorb or reroute fluid elsewhere.
I agree that the dealer may or may not be 100% straight with where all the fluid has gone, but given that this is certainly a warranty claim that will go all the way back to MoCo (commercially I mean) the dealer doesn't really benefit by not doing a proper job. Indeed, if you want to be really cynical about it, the dealer would probably be delighted to fill the workshop with MoCo subsidised work in todays environment. IMHO and experience with engineering machinery and associated warranty issues, I never touch it. If you do, you begin to open up split areas of responsibility, i.e. "HD" may claim that as the user had cleaned the bike they are no longer responsible.
One area that is worth checking out though is whether you are covered by this under warranty anyway. I wouldn't be surprised if the small print covers you for replacement parts and the fitting thereof, but you may well find that "consequential damage" is excluded.
I would encourage you to elevate it in the dealer to someone you know and trust (and who has the right level of authority), and ask them to explain exactly what you are covered for and what they intend doing about it BEFORE THEY START!
Something else that is worth noting at this stage. The focus so far has been the damage that this fluid does to paintwork and consequent corrosion problems, which is perfectly true, but brake fluid also damages standard seals used (eg nitrile o'rings) and insulation used on electric cables (PVC and PE). If a full reservoir of fluid was lying in amongst the wiring I would be concerned.
For fear of contradicting myself, my response may seem an overreaction, but given that you have paid a lot for a dream motorcycle I think this is justified. If this was a 5 year old bike, washing it down with soap and water would probably be the end of the story. Modern surface treatmens are very good should withstand a 1 off occurance like this (if it was the middle of the tank where even the slightest discolouration would annoy that would be a different case of course).