Lonewolf 50,
The slats retracted whilst the aircraft was still on the ground - that is, with 'weight on wheels' - which I'd suggest would normally be the condition under which reversers would be deployed on landing. Hence an oleo-linked switch would not have prevented the slats from retracting in this instance (given that the slat retraction was based on the reverser indication).
Protectthehornet,
Maybe they didn't firewall as they believed they had a problem with the inboard engines; certainly, at least a (spurious, apparently) reverser deployment warning.
A previous inflight (actual) deployment (Lauda 767 out of Bangkok) resulted in the engine blasting itself off the wing and the loss of the aircraft; maybe the BAW056 pilots were mindful of this.