A "negative acceleration" is an acceleration vector directed in the chosen coordinate system negative direction.
A "deceleration" would occur if there is a component of the acceleration vector which is OPPOSITE the velocity vector. A "positive acceleration" could be a "deceleration" is the velocity vector is a "negative velocity." Similarly, a "negative acceleration" would cause an increase in speed if the velocity vector is a "negative velocity."
So, the two terms are explaining very different relations. One relates to the coordinate system, the other relates to the velocity vector.