I use to have troubles with a smell in the foam ones. I use them as hatchers. It is the one thing my DW did compliment me on, is they no longer smell after 4-5 days.
I agree soap and water should sterilize. The USDA vet that came out here was insistent on using bleach at the 1oz to 1 gallon rate. That and spray Lysol so that is what I use. I asked about soap and water and she said " No, bleach is better"
So no idea why, I just do what I am told, sort of like when my DW tells me to do something, I am just trained to isten to women and never question I guess....sigh..