That statement about the first meeting seems really wrong. The AOA won't work without the plane moving through the air (preferably in the direction the nose is pointed). Because the vane has a counterweight inside it will be more than happy to sit at a random angle, until somewhere during the T/O roll the will start indicating AOA. The 400' sounds more reasonable to me, as it will give time for factors as side-slip due to crosswind T/O to dissipate.
That is a reasonable assumption, provided both vanes are working while on the ground. Frozen AoA, broken AoA, misaligned AoA...a first line of defense would be to determine if the AoA vane is bad while still on the ground.