INSERT DELAYED isn't writing ANNOTATE_ROWS binlog event

According to the docs, INSERT DELAYED should generate an Annotate_rows event, but doesn't.

It seems to be disabled in the code. See sql_insert.cc:

      /*

        Annotating delayed inserts is not supported.

      */

      di->thd.variables.binlog_annotate_row_events= 0;

And

    /* Don't annotate insert delayed binlog events */

    thd->variables.binlog_annotate_row_events= 0;

Why is that? Why can't the annotate event still be written and ignored when/if needed?

We really want to see as many rows events annotated as possible, for monitoring purposes.

Please advise if it's possible to fix this.