That isn’t the broken windows theory. They are saying that people that steal a backpack are likely people that often steal backpacks, so arresting and prosecuting them helps to prevent their individual future crimes. The broken window theory is that visible signs of petty/minor crime and disorder encourage other people to commit additional (and more serious crime) that they would not have committed.

So the broken windows theory would say that seeing graffiti and panhandling would signal to other people that the area had a more general sense of lawlessness, that criminality was more normalized, and that if they commits crimes they would likely not be punished. However, the broken windows theory has been pretty soundly debunked and leads to tons of discriminatory targeting. [1][2]

[1] https://www.nydailynews.com/opinion/ny-oped-break-the-broken...

[2] https://www.pbs.org/wgbh/frontline/article/the-problem-with-...