I'm so fly....I Neverland.
Being able to see up without exposing one's face is the reason behind the shape of most "climbing" style helmets. Smaller brims allow this to happen. As always, standards can vary by location and it's always a good idea to consult with your AHJ regarding the how and why of safety requirements.Who set this requirement ?. My research indicated there's no requirement for a harness when in a mast only lift, only used when in a boom lift.
As well, we only require a hard hat when there's work going on overhead and a potential for a dropped part or tool. When I'm focusing as example I do not wear a HH as I need to be able to see overhead.