As Jeff said, the idea of accenting the second stroke is not to be able to play that particular dynamic rhythm, but in order to emphasise the control over that second bounced stroke, rather than, potentially, relying completely on the bounce for it.
You would practice it as an accent, but only to develop that level of control over the second stroke.
The first stroke is presumably already controlled because it's essentially the same as the single stroke, so there's not usually any worry about how that sounds, but since the second stroke is considered to be weaker, practising it in the way Jeff (and
others) describes ensures that the second stroke can be properly controlled, to ensure an even sounding stroke.
Similarly, you can focus on being louder as you get faster, to counteract the tendency to reduce intensity of the hits as you increase the tempo. The idea is not to play double stroke roll like this all the time, but to develop the control to be able to play faster at the same volume/dynamics as you do when you play slowly.
Interestingly (to me), Dr. John Wooton talks about practising with brushes or on your leg to develop the controlled double strokes, but then goes on to say that you get more even sounding transitions (from slow to fast) by starting out with bounced strokes. Video
here. The demonstration begins around
1:15.
For me, I see the controlled strokes as being good for practising, controlled bounces more for actual playing.