If it's dry reef rock, it'll be full of dried out boring sponges and clams which will rot in your tank, immediately dumping phosphate and nitrogen into your system. If it's Florida "mined" rock, it's sat underground for millennia absorbing who knows what. I have Florida mined rock where coralline still won't grow on it after years in a tank otherwise completely awash in coralline.
Personally, I bought Fiji dry rock, soaked it in vinegar for a day to soften the surface layers, scrubbed off what I could of the biologics, soaked it in bicarb for a week to neutralize the acid, scrubbed it again and picked as much dead life out of the holes with tweezers as possible. Then I kept soaking it in a weak bicarb solution with a powerhead for flow, changing the water weekly, for about a month until the stench decreased to minimal.
The real issue with the reef rock is the retained biologic materials. All of the dried protein and DNA in the dead organisms immediately become ammonia/nitrite/nitrate and phosphate upon rehydration.