yes. if you ask me why people say nems have to go into an established tank, I’d tell you “I have no idea.” I have on many occasions put nems in a newly cycled tank. It’s really about how good you are as a reefer keeping things stable if bad things happen (as is more common with a new tank).
I have also put them in QT tanks that weren’t cycled for cipro treatment for 10-14 days. Granted, I was doing water changes almost everyday for the treatment.