I'd say it's no less important than pearl ... which does next to nothing, unless it's helped by cream. And if pearl DOES appear to cause shimmer in horses like Balitor - who carries a single pearl gene and shimmers like wildfire, but is bay - everybody says 'Oh, he's just shiny, it's not the pearl gene, because pearl has to be activated by cream.' ... Stick to the rules, and deny even the possibility of evidence from your own eyes. Sigh. How can science be driven by the refusal to consider anything new?
What? A great horse can ABSOLUTELY
... also be a wonderful color!