Tesla advertises on their website that they have over 100,000 employees, and they received over 3 million unique applicants globally in 2021. So their positions are highly competitive, and they are interested in only hiring the best and those who are determined to do whatever it takes. So, there are two reasons they may ask if you are available in the next few days. One is that you made it to the next round, or two would be to ensure you would do anything it takes to make it to the next round. So when answering this question, don't hesitate, and try to be as flexible as possible with your availability.
