if you press 1-9 in spectator mode you still can select items

try pressing 1-9 does work in spec mode (but scrolling doesn't)
you shouldn't be able to select stuff by pressing 1-9 (and eventually throw stuff away with Q) cuz there is no inventory hotbar still the tooltip shows at the place where it says (slot 1) "Diamond Pickaxe" (slot 2) "Bow" etc...