I haven't confused r with g. I think you may not have thought through what these quantities represent. r is the return on capital. An asset worth A returns A*r per year. This says nothing about wether A increases or decreases. You can use your capital income to buy more capital assets. But you can also use labor income to buy more capital assets. Basically the argument only works if you assume all capital income is saved, but no labor income is saved. But then the savings rate is doing all the work.