Long time I don't fly one of those...
What I remember is that in those airplanes, performance is usually referred to a fixed weight, typically MTOW. They don't bother in giving multiple tables for different weight ranges.
For the same power setting, TAS should increase when weight decreases. According to your 172 POH, this is at the rate of 1 kt per each 150 lb decrease. In the other one there's nothing written, Right? It can be either because they forgot to add the note or because the effect is negligible in that airplane.
Just guessing