Waving from the window

This film was brilliant and I loved Jason Watkins' performance. I didn't even recognize him until he had his makeover, then I yelled out, "It's the guy from 2012 and W1A!"

The only moment that threw me off was when Jefferies came home after Tabak had been arrested, and he stopped and stared flabbergasted at the window and when we see what he is looking at it's the ghost of Jo waving at him from the window. This was after we had heard that Tabak saw her wave from the window and interpreted this as a flirtatious invitation.

At this point I still did not know that this was based a true story so I was trying to second guess where the director was going with this. For a moment I thought the reason they were showing Ghost-Jo waving at Jefferies from the window while Tabak is saying she waved at him, was that they were going to sucker punch us at the end and say, "Fooled you! Jefferies was the killer all along." But within a few more minutes I realized that wasn't going to happen.

But I am still confused about why that scene was in there. Was it just for the pathos and to show that Jefferies was a compassionate person?