Tested with org-mode version 9.7-pre.
Looking at section 'A.7 Special Agenda Views' of the info org-manual.
It is stated that 'tags-tree' searches can set
'org-agenda-skip-function' to some function that decides on the
visibilty of each match. For what I gathered, by setting up something
like this,
(org-add-agenda-custom-command
'("b" tags-tree "some-tag"
((org-agenda-skip-function 'my-skip-function)
)))
, and then calling 'org-agenda' and selecting the 'b' entry.
It does not work, and 'my-skip-function' never fires after the request
is made. It works for some types of special agenda views though, like
'todo', but not with 'tags-tree'.
Is this a bug?