Slats impact on lift
Leading edge slats have very little impact on the lift generated at low to moderate angles of attack. The motivation for leading edge slats is to extend the lift curve at higher angles of attack to push the stall point to higher AOA / higher lift. As such, extending leading edge slats has very little impact on trim pitch attitude.
Making an approach without slats extended will require a higher approach speed and thus a lower pitch attitude in order to preserve margin to stall.