Looking at the explanation, it assumes that starch is lost to the water while cooking (which is plainly obvious if you look at the colour of water used to cook rice and/or when rinsing sushi rice before cooking), whether it looses a full 25% of the available carb content (starch) or not I don't know and probably depends on the rice in question and the cooking conditions.
There may be some additional benefit from the slower cooking process too which allows more cross-linking (iirc) to occur which makes some of the starches either harder or impossible to digest thereby stopping them from being absorbed.
YMMV, can you do a controlled experiment and tell us how it works?