The ssl shutdown is handeld in 'ssl_filter_io_shutdown(..)', wich will be invoked as a cleanup handler. But the cleanup handlers will by invoked _after_ 'shutdown()' is called for the socket, disabling any further write operation. So the client does not recieve any ssl shutdown message. (The mod_ssl default is SSL_RECEIVED_SHUTDOWN) That behaviour can be verified using ssldump.
This is fixed in the forthcoming 2.0.49 release; thanks for the report.