Gap between bailable warrant and non bailable warrant

It all depends upon the advocate/lawyer arguments before the court. If the advocate justifies to the court that even after BW the witness is not deposing before the court then the advocate can inform the court to issue NBW on the next date so that witness summons can be issued by the court fast

so you mean to say that the court will not wait for any report from the Police whether the already issued Bailable warrant served to the accused or not

Court will only after police report from the police will decide to issues NBW on the witness. But it also depends upon how your advocate argues this case

It's not against the witness, it's against the accused. Any difference in the approach by court?

The court may wait for the police report about execution of bailable warrant,  and after that the court may decide about issuing NBW