probably has a lot to do with the way they are harvested and transported. inexpensive fish don't get the royal treatment like the more expensive ones do. Mine happened to all be suicidal and jumped. Not one died in the tank.
I generally quarantine for a few days to a few weeks depending on species. Chromis usually get a copper dip, a freshwater dip, and into the tank they go. I suspect the QT method of 2 weeks' isolation I've done in the past accelerated their stress levels, and losses prior to the dip, dip, introduce to DT method were considerably higher. They need flow, hiding places, and apparently a need to feel an escape route is needed.
Being surrounded by glass, including a BB QT tank looks to stress them.
I have no basis in fact, just my observation and personal feelings.