The book is a gentle introduction to pf. The details about
set loginterface and why it is useful, can be found in the
pf.conf(5) manual page.
If you follow my advice, you will see the blocked packets, the protocol (tcp or udp) and the port number in the tcpdump on pflog0 xterm.
If you don't want pf to block this type of packets, then you have all the information to create an additional rule that will allow this kind of traffic.
Instead of giving hungry Daffy a fish, I am just trying to teach how to fish by yourself