I think that was an intermediate model. The author updated it, then Gurobi solved the new model to optimality (i.e., the bound became equal to the value of the best solution found).
> With this improved model, I tried again and after ~23 000 seconds, Gurobi solved it to optimality!
> With this improved model, I tried again and after ~23 000 seconds, Gurobi solved it to optimality!