Well, considering this:
And some other confirmations via inquiry to customer service of the new PC options in other posts (don't remember where they were to dig them up), Gloss White would be all white everywhere on the saber, when selecting it from the finish options on the main ordering page.
However...
You could elect to go through the
SF Customs Shop for a custom powder coat scheme, where you could keep the black detailing via simply not putting anything on the anodized parts, or with a Mirror Black PC in those areas (to match the shiny finish of the Gloss White).
IRCC, it was said that they're doing it this way to "lighten the load" on the Customs Shop, since the majority of requests were just simple full-saber powder coats.