OK - just to clarify......
Both at Bristow and British International it was/is standard to disengage AFCS on a moving deck.
However - it was NOT standard at Bristow (one of the largest operators of S61's in their day), and is not standard at BI (and presumably was not at their predecessors, Britsh Airways helicopters) to disengage it while taxiing or stationary on solid ground. So an awful lot of policy makers/training captains/line trainers (which I am not....) over the years must have found it acceptable. Also I can find no reference in the Flight manual suggesting or requiring it.