If using the hot shot method then no need to sterilise as it will always just hold boiling water. Used the same over for 1 year & no issues.
The instructions definitely don’t say just that. They say to wash with hot soapy water and then sterilise. 1 of the ways you can sterilise it is in boiling water though. It would need to boil for 5 minutes to be sterile.
This is if you pour formula in it to cool down. If you’re just cooling the boiled water which most people do then it doesn’t need sterilising each time x
I clean my nuby bottles with warm soapy water, dry and then sterilise with UV steriliser. Technically all can be also sterilised with steam steriliser if you want Except the white lid (the one that gives you info on the temperature) that should not be in contact with water for too long, just enough time to wash it
Just use the hot shot method then you don’t need to sterilise x
I clean mine with hot water and soap and then use cold water sterilisation tablets