They could still get money out of him, if it goes to court.
They have probably worked out while they are trying to shaft him for some of his bond and he has just shafted them.
They get to keep 3/4 of his bond in rent payments and if they want to charge him more $ up and above what they already have and head to court over it, they will actually have to prove they are right.
Not my cup of tea but I did get royally shafted once back in 2006, when I broke lease 3 months early, the real estate agent relisted the house at $80 a week more than I was paying. It listed for $330 a week and no takers, it was dropped $10 every couple of weeks till someone rented it at $270 a week.
I paid rent for that place for 10 weeks after I moved out, only 2 weeks short of the full year. I questioned the real estate agents approach and she said it was under-priced and she was seeking rental market value.
I lost my bond and paid several extra weeks rental to keep myself right... in hindsight I shouldn't have paid and let her prove her actions were ethical in court, if she decided to come after me.