All good. I use interpolation in my real project. This is just a demo to test the toolkit with a toy model and make sure the toolkit functions give correct results. You can notice that I have double coded everything with custom-made functions that run on cpu (with the exception of the panel simulation). The results are identical across toolkit and my own cpu implementation.
Since I don’t have time to code the interpolation method on the cpu, I am not using it in this test. I just trust the VFI-Toolkit 
P.S. With this method I found a previous bug in the distribution code.