I've done it plenty of times. You will have die off from scrubbing the rock and depends on how much rock and how big your tank is you might go through a mini cylce, but that didn't bother me too much. Just my experience.
Iv done it also and seemingly it does not create a swing in the tank. I usually do it only when a deep cleaning is due! In the past I used to do it alot, until I got my bio under control and established. I see no problem w it. When Im curing I will do some scrubbing only after I eyeball the pieces. Obviously make sure your not scrubbing any minute crustations,like baby mushrooms. GOOD luck pally.
I did about 20lbs Tuesday with a stiff plastic brush, in a tub of old salt water & plopped it back in, man it was bad. Depending on the size of you tank & amount of LR Just do a little at a time, do it in the water your changing out in also.
I have never removed my live rock from the tank. I use a bottle brush to remove cyano and lightly clean the rock. If you have sponge on the rock and they trap air when removed --- they will die off. Sponge is the most valued filter in your tank --- a turkey baster will blow the rock clean after a light cleaning.
IMHO -- I have a problem with tank water going to a sump or other device that will trap waste before it goes through a filter. Water should also be cleaned by a filter before being used for water movement or this waste will collect in the small crevices in the rocks etc. I use polyester fill in a canister filter basket to remove small particles and change it once a week to reduce nitrates. My water changes consist of changing 2-gallons of water in my filter once a week!