My previous post was not accurate since I was not able to check the B 737 NG AFM.
Basically the concept of CAT II and III has all to do with the definitions of “Fail Passive” and “Fail active” autopilot systems.
According to the B 737 NG AFM one needs both Autopilots to do a cat II and this implies that an automatic landing is the only option.
If a technical failure arises AFTER you have passed the approach ban then you have to abort the approach.
On the B 737 EFIS a cat II single channel was allowed and I do not see why it has changed on the B 737 NG.
Maybe the increased risk of tail strike has something to do with this ???
Anyone can shed some light on this ?