We don't even know if it's actually a 1.5 frame latency for real because the test didn't try to establish that. The author said it looked like it was 1.5 frames, but that could be a coincidence. It just looks like a 1.5 frame overhead. It could, in reality, be a constant time overhead rather than a function of frames and so would be fine with a lower frame rate.

Tearing would affect everyone that uses a computer with X11 but your proposed example of a TV with 30i refresh rate would only affect the tiny subset of users that use a CRT television as a monitor, right?