From the website..
"Hybrid Health Check included
A Hybrid Health Check is included in all services. This includes a technician testing your entire Hybrid system and then providing you with a written report. For eligible vehicles, the Hybrid Health Check provides a one year 10,000 mile warranty on the Hybrid Battery."
https://www.lexus.co.uk/owners/benefits/#benefits-section
So, the health check is part of the service, even on <5yr old cars (mine just booked in for it's 1yr service and was advised the health check would be done and report will be provided) but clearly the extension of the warranty doesn't kick in until after the 5th year (eligible vehicles)