Safe?... What is "safe"? A complete absence of hazard? Not possible or desirable.
One wants to minimize hazard and avoid unnecessary risk. If the helo is securely on deck, set at appropriate ground idle and controls secured against movement, does the PIC increase hazard by leaving the cockpit and surveying the landing area? Some operators think that's a bad idea, some have explicit requirements to allow it. I want the option, was taught the proper methods of doing so by the US Army.
Not a legal expert, but I believe the pilot and employer assume all responsibility for helicopter operation, including while the pilot is not at the controls,