I don't think they are equal. Because in the process of increasing the force, the reaction force will not increase immediately. Only in the inertial system is the force equal to the reaction force.
For example, if you put a 1 kg object on the rubber block, the force of the object on the rubber block must be less than 9.8 N at first, and then when the object is still, the force of the object on the rubber block is 9.8 N
The reaction force is equal and opposite at all times as required by Newton’s 3rd law. If that were not the case then momentum would not be conserved. Let’s analyze the example more carefully.
There are two forces acting on the object. There is the 9.8 N downwards force of gravity (the weight) and the variable upwards contact force.
The third law pair of the 9.8 N weight is an upwards gravitational force on the earth. This is also a constant 9.8 N, so it is equal and opposite at all times.
The third law pair of the upwards contact force on the object is a downward contact force on the rubber block. These forces vary over time, but at each moment they are equal and opposite to each other. When the object first touches the block the forces are much smaller than 9.8 N, but as the block rapidly decelerates they quickly become larger than 9.8 N before reducing back down.
The contact forces are independent of the gravitational force except in the special case when the system is in equilibrium. It seems in your scenario that you are trying to analyze the contact force and the gravitational force as a 3rd law pair, which is incorrect. Third law pairs always act on different objects and are the same “type” of force.