@Bloggs
"Say what? What is "neutral"??"
I guess he is referring to the trimmed 0 point of the control wheel's roll / aileron axis. Aileron trim can be used to offset this datum, but the AP will never use aileron trim and you should never touch it while the AP is engaged, as otherwise, as you disconnect the AP, the control wheel will 'jump' to this new datum and initiate a roll!