Unexpected difference between functions plots involving oscillatory integrals

Questions
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1

I’m trying to plot three functions involving oscillatory integrals.

I also implemented these functions in Python using SciPy, and the plots there look similar for all three functions. However, in Mathematica, the curves differ. What is the reason? Which one is correct? Python or Wolfram?
this is the link of the Python code which you can run it in colab

Here’s my code in Mathematica 11:

Open in Wolfram Cloud ↗
2

Try using “MultiPeriodic” method instead of “GlobalAdaptive” i would guess is better for this type of integral.

3

I took a symbolic look at the three functions to be integrated. The first two are identical. The third is not identical, but it differs from the others by an odd function, whose integral between -30 and 30 vanishes. Is this just a test for numerical algorithms?