if i log into ios26 backup with new iphone 16 with it force update to ios 26?

ios 26 ruined my phone & i ordered a new one. at the store i was told that unless i create new icloud on iphone16 pro max which has ios 18 pre-installed, it will force update to ios26 from my old phone backup when i log in. i don’t mind making a new icloud and manually transferring info but its been years and all my other devices are on one icloud. is this true? im clearly avoiding ios26 & my current iphone is 15 pro max with ios26.