It depends on how close to burnt the rice on the bottom is. If it is actually burnt it will permeate the whole batch. It usually singes pretty good and is not desirable to eat. If you don't get any rice stuck on the bottom you probably didn't get the pot hot enough to get it back to a boil fast enough after putting the rice in to make the rice pop (whew, long sentence). In other words you want the stock and meat at a hard roll when you put the rice in and this inevitably makes the rice stick to the bottom and slightly scorch. So we don't scrape the bottom after we cover it and cook the rice a bit in case there are some burnt grains of rice. One burnt grain losened from the bottom can ruin the whole batch.