If the wind changes during the long period ,let's say 1 hr ,change of 50kt head wind to 15kts head wind during 1 hr is not a significant change it is very common in enroute flt. You don't have to compensate thrust for that wind change. But Windshear is a different story. Windshear is a sudden change of wind velocity or direction. Aircraft(mass) has an inertia.
Even though there is a sudden change of wind from head wind to tail wind that aircraft wants to maintain that condition like a stone fixed in the air. In that case tail wind will change the atmosphere around the aircraft. Head wind to tail wind. It will reduce the IAS suddenly. If you don't adjust thrust ias of the a/c will increase eventually. Reverse will happen if wind changes from tail to head wind.
It is a problem of inertia not the stabilized condition.
Hope this will be a help for your question.
See you around.
I had had that same question in my ppl period.