In SoCal, I was at the West LA service center in mid-Dec 2018 as they were prepping the new showroom S to go to the Century City Mall location, then saw it there a week later. Same one in the mall showroom as of two weeks ago - 4 months. Went to another showroom this past weekend, and the S100D also has a sunroof, opened and on display as an option for prospective purchasers.
But, aside from those, the sunroof isn't necessarily an indicator of how long a showroom car may have been in stock, as I have heard from two people I know that just recently traded in older S's for new ones, for in stock verified "2019" vehicles, that they purchased 2019 S's with sunroofs. They were told S's still being made with sunroofs for 'in-stock' inventory fulfillment, but just not available to configure and order online (which seems to comport with the reports that a person can still special order with a sunroof).