This is only true if there were no fees associated with investing, which is ridiculous. If you went to a stock broker with a dollar per day, you would be very lucky to end up with $0.01 in equity that day.
That would reduce the ROI, because doing it often (every day) approximates continuous exponential growth (e ^ x) while doing it in batches reduces to power growth (1 + r) ^ x. See the effect this has in the example given here: