Is it normal for ALT dispatch companies in Japan to reach out to your previous employers?

I applied to a smaller ALT dispatch company known as A to Z. The interviewer wanted to know if he could contact my previous employer. I few years ago I did one contract with Interac right before the pandemic. It's the only previous experience I have teaching in Japan( although I did spend a year and a half teaching in Korea, and a year working as a building substitute in a large city in my home country.) The dispatch company I applied to wants to talk to them now. Is this a normal thing to request?