That is exactly what Redline says about their racing oils. Use them in mixes of 18:1 (karting) to 50:1 (MX), and as lean as 100:1 if the engine is designed for it.
A oil quality benchmark is the leanest mixture you can use without immediate harm to the engine. In this vieuw, amsoil 100:1 is a quality oil. The manufacturer says it is suitable for 50:1 up to 100:1 mixes. I would never take the leanest possible mix. Engines run on an oil film. Synthetics allow 100:1 because they build up on the metal surface due to their extremely high polarity, which makes the oil cling to metal. Yet more oil will expell waste producs much faster. This waste is something you do not want in your engine. It has to be purged, which only happens at higher oil content mixes. If purge cycles are slower, you need to rely heavily on evaporation, acid buffering (base number) and cleaning properties of your oil. In addition to that, no purge is ever completed, because the oil cannot scrub the surface. Old remnants still refuse to let go, again due to the high polarity.
edit:
This polarity leads to quite thick oil films, as can be seen of this picture. I pulled the jug, and ran a finger over the piston skirt just once to check the amount of oil present.