"if you autoland single engine you are limited to idle reverse on an IAE powered 320......why? "
According to my FCOM only the A321 (IAE; not sure about CFM)has the IDLE reverse limitation with the additional limitation max crosswind 15kts. A320 does not have this limit.
My guess is it is a control issue with the longer fuselage?
mcdude (trying not to be techy...)