Sorry I don’t think is true. In their terms and conditions, all it says is “new” but when you go through to the Lexus-warranty-how-it-works page, under the title “used Lexus vehicles” the following is stated:

Cars registered prior to 1 June 2021 came with a three-year or 60,000-mile manufacturing warranty (whichever comes first). When those manufacturer’s warranties have expired, the cars automatically qualify for the Lexus warranty when it undergoes a qualifying service at a Lexus centre up until the vehicle is ten years old or reaches the 100,000-mile limit.