To be honest, I really doubt it was the intention to have the RFC 1918 address block in this example. You should ask Christos about it. An excellent pool for documentation and examples is one of the RFC 5737 blocks, for example, 192.0.2.0/24.
FWIW, this apparent and important fix causes conflicts to merge for etcupdate(8) on every single host that I updated recently.

In D56773#1309695, @zarychtam_plan-b.pwste.edu.pl wrote:

To be honest, I really doubt it was the intention to have the RFC 1918 address block in this example. You should ask Christos about it. An excellent pool for documentation and examples is one of the RFC 5737 blocks, for example, 192.0.2.0/24.

The change stems from: https://github.com/zoulasc/blocklist/commit/0719c4ce739aab8526b7c1456dc7a53110328152, committed by Christos. Using RFC 5737 blocks has been suggested, this change is in "the pipeline", mainly for the manual page.

EDIT: Corrected RFC number.

FWIW, this apparent and important fix causes conflicts to merge for etcupdate(8) on every single host that I updated recently.

As with most changes in /etc. This is the main reason I decided to omit it for the upcoming 15.1-RELEASE.