Need some advice regarding rotors

For context, I have a 2025 Acura RDX with about 9200 miles. I leased this car April of 2025, so it’s barely a year old. April of this year, I noticed my car was making a humming noise when I would reverse (specifically if it was raining). The noise wasn’t persistent so I didn’t think much of it. Today I went to the dealership to see if they can tell me why this noise comes and goes at times. Come to find out, my rear rotors are messing up due to the way “Acura designs them”, is what the guy the told me. He also said that my breaks warranty is only for a year and that if I want to get it fixed, I would have to come out of pocket about $900. Has anyone else had this problem before? My car is barely a year old and I don’t think it should be having problems like these already.. I’m also not a crazy driver.