Some points can't be answered clearly by the datasheet, my assumption is:
AAM. The question is if pulse skipping is implemented by stopping the oscillator or by ignoring clock pulses. The block diagram suggests the latter. If so, SYNC would still work in AAM, pulses are aligned with SYNC edge but some skipped with light load.
SYNC and SYNCO. According to the datasheet, SYNC is edge sensitive with no requirements for the pulse width except being > 100 ns. SYNCO is said to be 180 degree phase shifted, in other words its pos edge is centered between SYNC pos edges. Nothing is said about the pulse width which won't actually matter. May be it's 50% duty cycle. Surely not the inverse of SYNC in general, SYNCO also works with free running oscillator (EN/SYNC = 1).