Connected to pin 9 is needed for an always on installation on the non-GS/non-lite chips (IE, the older ones).. For the GS and Lite Series, while it will likely work fine with BT open/disconnected, it's always better just to tie it high (3.3v, IE, to pin 9) than to leave it open as an open connection is subject to interference/etc and may not always behave as intended.