While there is nothing in the books to indicate that there is no difference between the way angreal and sa'angreal work, there's also no indication that they work the same way. Considering that BS has RJ's notes, and therefore a huge pile of info we don't, I can't see how you could think that his thoughts are wrong. Not to mention the fact that I would think that the WT raid would have at least been outlined by RJ, likely including Egwene's theft of the sa'angreal, which would mean that RJ would have thought that she would have gotten some benefit from it.