The TLS RFC (5246) specifically states that this exists: This leaves a small timing channel, since MAC performance depends to some extent on the size of the da

The TLS RFC (5246) specifically states that this exists: This leaves a small timing channel, since MAC performance depends to some extent on the size of the data fragment, but it is not believed to be large enough to be exploitable, due to the large block size of existing MACs and the small size of the timing signal. So I guess you're right, they're just showing that a known theoretical attack is not quite as theoretical as thought.