I’ve only seen one screening, but how did DJ know to recommend running a scanning operation? I don’t believe the reveal about that detail happened until after they were on the Star Destroyer/bomber I forget the name of.
I don’t think DJ mentioned anything about running a decloaking scan; I think that was Hux that ordered it out of assumption that since their radar wasn’t picking up the transports already, then the obvious conclusion is that they’re being cloaked.