Q*R*H
There is no design fault. The 737 autothrottle is designed to retard on a handflown approach (autothrottle in) as well as during an autoland. Admittedly the former is not recommended due to the marked pitch change with power reduction on this type. I flew the MD83 and it was normal to leave the autothrottle engaged to touchdown as there was no pitch change.
The fact remains that the autothrottle is far from essential and does not require endless fail safe devices. If it misbehaves, knock it off.