Not specifically 747 but similar systems of the era used energy management as a basis for WS GA escape guidance.
Wind-shear detection is generally based on a change in energy, which could be modified by altitude; i.e. earlier trigger at low alt than higher up.
Wind-shear escape guidance (FD or AP), depends on the thrust setting - energy available. Some aircraft systems change from TOGA (reduced 1 or higher 2) to provide absolute Max thrust for the conditions.
The guidance logic balances the need to avoid ground contact by maximising aircraft perf for the thrust available (low alt), and moving away (through) the horizontal effect of the shear; i.e. comparing energy required vs energy available. In downburst conditions the priority is ground avoidance, best climb perf, but with less vertical shear component (more energy available) there is a tradeoff with speed increase to quickly avoid the area, this is also a function of altitude.
These systems differentiate between the normal GA (TOGA 1 or TOGA 2) mode and WS GA; where the latter could increase thrust and use a different guidance algorithm.
System switching would be aircraft dependent - auto thrust and auto WS guidance based on alerting, or manual re-selection of GA / thrust after an alert - which appears to follow Boeings philosophy of manual command, cf #8.