I think I may be looking at it from a different angle, although I follow your logic through and through.
What I believe it means is when 100 Mbps is recorded per second, that means the camera is approximately writing at that speed per second, no matter the frame rate of 24fps or 30fps.
So with that logic, I would suppose that it is recording more information for 24fps vs 30fps, but the quality is negligible.
Also, remember that the camera is writing approx. 100 Mbps, not exactly 100.00 Mbps. Therefore, with those six additional frames, you aren't getting a huge bump in quality if you stuck with 24fps instead.
That's my view on things. Although you did the math and may be correct, in the end I don't think it actually matters. :) You are still going to have the same quality whether you're in 24 or 30fps.
Cheers,
Dylan