I would agree with you and I also did research on neural networks when I was in college. I'm not sure if those downvoting you have actually done/seen neural network research. Deep learning is pretty engineering driven (as opposed to theory driven), right now.

I have a pretty weak understanding of statistics and from my perspective it was very common for grad students to also have a weak understanding (of course, those working in statistical learning theory had a strong understanding). This is a pretty ordinary occurrence - it shouldn't be surprising - this is sort of like pointing out that many theoretical statisticians have poor coding skills.