Troubleshooting mapatoms returning nil despite interactive functions

I want to make a function that returns interactive functions defined in a given 
file.

Studying mapatoms, I understand it applies a function to each symbol in obarray 
but doesn't collect results - you must accumulate them yourself.  Unlike mapcar, 
it returns nothing.

Have selected a file, but the output is still nil, even though there are
interactive functions loaded.

(defun mazella-smbp (smb file)
  "Filter symbol SYM defined in a specific file that are currently loaded."
  (when (and (fboundp smb)
             (eq 'autoload (car-safe (symbol-function smb)))
             (string= (symbol-file smb) file)
             (commandp smb))
    smb))

(defun mazella-agfun (file)
  "List all interactive functions defined in FILE."
  
  (interactive "fFile: ")

  (let (smbs)
    (when (find-file-noselect file)
      (mapatoms (lambda (smb)
                  (when (mazella-smbp smb file)
                    (push smb smbs))))

      (message "Interactive functions: %s"
	(seq-filter #'commandp smbs))
      (seq-filter #'commandp smbs))))