Thanks Ihor, I sent a new patch with your comment included verbatim, and also added a ChangeLog entry.

On Tue, Feb 7, 2023 at 12:47 PM Aaron L. Zeng <me@bcc32.com> wrote:
* org-agenda.el (org--batch-store-agenda-views): Fix treatment of
lambda functions used as custom agenda commands.
`org-agenda-custom-commands' entries may specify a custom function
instead of a symbol like `tags-todo'.  `org--batch-store-agenda-views'
behaved differently from `org-agenda' when that custom function was
defined as a lambda rather than a symbol, incorrectly treating the
lambda form as a list of agenda commands.  Instead, use the same test
as `org-agenda' does to determine whether the command is a series.
---
 lisp/org-agenda.el | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/lisp/org-agenda.el b/lisp/org-agenda.el
index 1d1f2271b..49f93c338 100644
--- a/lisp/org-agenda.el
+++ b/lisp/org-agenda.el
@@ -3525,10 +3525,13 @@ This ensures the export commands can easily use it."
   (let ((cmds (org-agenda-normalize-custom-commands org-agenda-custom-commands))
         (pop-up-frames nil)
         (dir default-directory)
-        cmd thiscmdkey thiscmdcmd match files opts cmd-or-set bufname)
+        cmd thiscmdkey thiscmdcmd match files opts cmd-or-set
+        seriesp bufname)
     (save-window-excursion
       (while cmds
        (setq cmd (pop cmds)
+              ;; series:     (0:key 1:desc 2:(cmd1 cmd2 ...) 3:general-settings 4:files)
+              ;; non-series: (0:key 1:desc 2:type 3:match    4:settings         5:files)
              thiscmdkey (car cmd)
              thiscmdcmd (cdr cmd)
              match (nth 2 thiscmdcmd)
@@ -3538,8 +3541,9 @@ This ensures the export commands can easily use it."
                              (format "*Org Agenda(%s)*" thiscmdkey))
                        org-agenda-buffer-name)
              cmd-or-set (nth 2 cmd)
-             opts (nth (if (listp cmd-or-set) 3 4) cmd)
-             files (nth (if (listp cmd-or-set) 4 5) cmd))
+             seriesp (not (or (symbolp cmd-or-set) (functionp cmd-or-set)))
+             opts (nth (if seriesp 3 4) cmd)
+             files (nth (if seriesp 4 5) cmd))
        (if (stringp files) (setq files (list files)))
        (when files
          (let* ((opts (append org-agenda-exporter-settings opts))
--
2.38.1