ElNull
They don't, but the effect on the inboard spoilers seems to be that the aircraft requires a bit more nose up trim with spoilers deployed. If the autopilot is then disengaged, the spoiler bias is removed (i.e. the spoilers retract) but the nose up trim still exists, which will mean that pitch will increase slightly and that should arrest the descent to some extent.
PS: Not 787 rated, just guessing based on similar behaviour on other Boeing aircraft, as well as what the note says (slight forward pressure required means that aircraft is slightly out of trim in the NU direction).