I used the "strict-order" flag to set my DNS servers to work in order per this post.
I expected queries to #1 (CloudFlared - 127.0.0.2#5552) to be more prevalent than queries to #2 (Unbound recursive only - 127.0.0.3#5553).
Queries to #2 were much more prevalent than to #1. To address it, I reversed the two IP addresses in the Pi-hole web interface. Now it is behaving as expected, albeit with the two servers in "incorrect" order relative to how they are functioning.