Update: I don't know where you're located but according to racv.com.au, all CX-30 variants feature "rear parking sensors" and the "Vision Technology" package adds front parking sensors (in addition to other features). Note the source appears to be Australian.
My Mazda CX-30 also does not have rear parking sensor. I did not pay attention to it when I was buying it and now I think it would be useful. But the car is good, so it's not so important. The only thing I don't agree with is the price. I think it’s inflated.