"How do you determine the level of infection? I'm not convinced that digging around the edge of the infection will give you accurate information at all times."
All times? What are you saying; you need a guarantee or you won't look? Of COURSE you won't get it right at ALL times, and you don't have to be convinced. But you do have to make an effort at gathering relevant data to have any credibility at all.
[ QUOTE ]
...working arborists certainly have a bias to be risk averse with respect to trees threatening buildings or people.
[/ QUOTE ]which working arborists? Not all, certainly! My bias is toward preservation, if I must have one at all. It's easier to be risk-tolerant with more practice at detailed assessment. If inspecting is too much work, or too scary/uncertain, then the tendency is to be a defensive assessor, like the attached.