Meteor Preload adjustment can void warranty??

I own an RE Meteor 350. Bought it in March. Went for my second service at 3100 kms (6 months done). When I asked them to set the suspension preload to what the manual recommends for Rider + Pillion settings they warned that this could void my warranty. Is that the case or is the service center trying to scam/scare me?

Has anyone had any similar experiences?