(defun org-set-tags (&optional align-all align-current)
    "...
  ...
  ALIGN-CURRENT is obsolete and should not be used. When non-nil,
  set ALIGN-ALL to `current'."
    (let ((align-all (if (null align-current) align-all
                       (warn "Deprecated call to `org-set-tags', which see")
                       'current)))
     ...))

That will work. Good idea!

I'll first patch maint, and then this in master.