[R-meta] p-values in multivariate, multilevel models

Dear Colleagues,

I recently came across the following meta paper
[https://doi.org/10.1080/19345747.2021.2009072].

I wanted to make sure that I correctly understood the p-values for
categorical variables in Tables 5-10.

What I am not sure about is whether each p-value is a joint test regarding
whether the conditional means are (A) significantly different from one
another OR (B) significantly different from 0?

Which one (A or B) is more important, if we want to find categorical
moderators that explain heterogeneity the most?

Sincerely,
Tim M