Maybe, or it might just speed up the drying on the surface and trap more moisture farther down. I know on hotter days I have seen concrete contractors wetting concrete sidewalks the day after it was poured? and or and covering it with plastic. I am not sure But I think It sets up better if the process is not forced with over drying. I would probably just wait and be careful in the room so you don't cause any stains or anything. those are just my thoughts about it
. Ask the person that told you to wait before sealing if the dehumidifier would be wise. They might say it will be fine with grout.