I really don’t believe it. At some point it was even a suggested workaround to intercept requests to port 53 because the Shield or its apps were not honoring your network’s DNS configuration. Which would be similar to the pihole not being in the picture at all.
If it’s really working for you, I suggest telling the community how you’ve done it because this question pops up every other day and the answer is always the same.
It’s quite absurd to suggest this is the reason as if the scientists involved in the study would completely overlook the most basic of ideas. It’s a bit of a Dunning Kruger and hubris love child.
Not to mention that the—very short—article even explains the mechanism which refutes your idea.