A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Robin Stuart
Date: 2019 Mar 21, 05:55 -0700
You are correct. The figure you attached also appears in a paper by J.E.D. Williams published in the Journal of Navigation.
However as demonstrated by Ian Cook only one of the numbers in the diagram is actually generally correct. Cook's paper also provides an answer to my question "Is the probability that your true position falls inside it still 25%?"