Moving Average Filter's Magnitude Response

I am working on filtering of data using the Moving average filter in MATLAB.

My data is recorded temperature values on the Y-axis and Time(in seconds) on the X-axis

(I’m getting the magnitude response curve of the Moving average filter as attached)

The shape of the curve seems fair for the moving average filter, according to the theory but,

I want to ask, why am I getting all the magnitude value for MA filter positive? (is this correct?)

Implementing other filters like Butterworth etc. on the same data gives the magnitude values to be negative (image attached)

Here is my MATLAB Code for MA (if it helps)

%T.Temp is table column containing Temperature values in double format.

MovAvg = dsp.MovingAverage(5)

movAvgOut = MovAvg(T.Temp)

fvtool(movAvgOut)

%Gives output the first image I attached

Any help is appreciated.
Thank you.

Ps – DSP is not my field. This work is part of a bigger project i’m involved in, and need some help. Please bear with me if I sound irrational.