Either angels are lazy with clean-up or they’ve left the mess to remember him by
Never change, fandom!
Minor sets like this are usually dismantled and put in storage during hiatus so the studio can use the lot to film another show. That means they had to rebuild the set and carefully place the rubble back where it was. It would have been easier for the props department to use the original, undamaged jail set. Using the damaged jail set made more work for them which means they purposely did this to remind us of Gadreel and his sacrifice
They also very purposely placed the camera down by the floor to get the rubble and the destroyed prison bar lattice in the frame. It was very much the Gadreel Memorial Rubble.
I almost wonder if we’re supposed to be noticing the destruction left behind by Hannah’s refusal to listen to anyone who goes against the “rules”. Gadreel took that extreme measure because Hannah wouldn’t truly listen. Daniel ended up dead in part because Hannah didn’t want to listen to him any more. Adina said she and Daniel would never get a chance to argue their freedom from a prison cell, and I think she was right….look what happened to the last guy who tried. And it looks like we’ll be seeing Adina facing off against Hannah again this week.
I’m getting the idea that a lot depends on Hannah learning how to listen to the wisdom of others and paying close attention to her choices so that she can learn who she (and Heaven as a greater unit) truly is, like Daniel advised.