HRC wouldn't have made something like this without extensive testing to ensure safety, this would be too big of a liability.
HRC stuff is race stuff - and I mean that in a legal sense, like not road legal or road approved race stuff.
The DOT rules for brakes are pretty old, and come from a time when motorcycles were mostly cruisers and standard JDM bikes, and when brake systems tended to leak or break down quickly due to exposure and materials of the time. So they mandated having quite a bit of extra brake fluid attached to the system as a compromise measure.
Because modern sportbikes are so very different than standards or cruisers, the rear brake makes up much less of the overall braking power of these bikes, and when you run only on a race track, almost nothing (you only use the rear when dirt farming, i.e. off track expedition). Because of this, race bikes need only a minuscule amount of resevior space for brake fluid, for packaging, simplicity, and weight reasons.
On the street it's not really going to get you anything, but given the reasons above, doesn't really make you exposed to dangers either, given you did the mod correctly. But in absolute terms: it's not road legal, and it's not as 'safe', technically.