Hi there!
At the time of my interview barely any IR-2/CR-2 visas were being issued (back when COVID was at its peak), that definitely helped me be able to have the visa issued on the same day since they were not processing any other visas at that time.
Also another thing that helped was asking if it would be possible to have it issued on the same day, had I not asked, we would have probably had to wait 2 weeks like everyone else.