Let me reiterate.
Drive
Full brake
Reverse
Let go of brake
Rolls forward
Take a video of it. I still suspect you're wanting instantaneous engagement of the gear, and that just doesn't happen. Give the car the fraction of a second it needs to engage the proper gear.
I would also point out that your transmission is not a brake. You shouldn't be leaning on it and expecting it to hold you from rolling foward (or back, when in drive) on any kind of incline. Emphasis on 'any kind,' because if you've properly halted the cars inertia in the other direction and are on level ground, it's not going to roll forward in reverse, even if the reverse clutch pack is totally smoked.
Hondas, moreso than anything else, actually have a tendancy to pull a little more at low RPM. On level ground, they will often actually try to roll forward in neutral. A lot of FWD's will actually spin the wheels in neutral if you put them in the air; Honda are just the only ones I can recall trying to make a slow getaway on the ground.
Basically, if there is truly no driver error here, then slipping in reverse only would indicate a problem with either the clutches that engage gear, or the hydraulic circuit that actuates said clutches. Generally low line pressure would likely affect more than just reverse.
If it is, in fact, a problem with the reverse clutches, then, well, I'd have to say that they got that by...yup, driver error. I've never heard of a reverse gear failure due to worn clutches; parking lot maneuvering just doesn't subject them to the same stress levels that your forward gears (especially 1 and 2) will see.