Using the default, performance BIOS, the card does not include the idle-fan stop feature. This capability is only available through the second "quiet" BIOS. In both these modes, the pump will be running, however, and it will be the main source of noise for the graphics card, especially when idle.TPU ASUS RTX2080Ti Matrix review
I believe noise can't be so loud.
Even full custom watercooling PC with D5 pumps you usually hear pump on 4-5 speed.
To cooldown CPU and GPU and to prevent any noise people usually use completely silent fans as Noctua NF-A12x25 PWM they could work silent up to 1500-1700RPM without noise in closed case and Dual D5 pump reduced on speed 2 or up to 50% speed. On that way pumps offer good flow in silence and if one die other continue to work and prevent overheat.
Pumps can't stop in any situation. Only fans maybe could stop if heat is minimal, but pump need to continue to work.