The algorithm is currently tuned for producing clean moving edges that accurately reproduce the sharpness of the original. Thus, in the pinwheel and spokes pattern, you'll see that the edges (especially nearly horizontal) have much less aliasing than the linear and lanczos images. And cubic is just a mess on the spokes and pinwheel patterns.
Lanczos, in this case, degrades into a 8x8 separable kernel.
The earlier problem with sparklies in high-frequecy areas (tight ridges/valleys) has been mostly mitigated. The remaining sparklies fall into two categories, one category that is affected by a tuning parameter that trades off sparklies and aliasing, and a second that is fundamental to the upsampling method.