I could also see them extending the sale to be able to include the Agnes Varda set that is being released on August 11.They have done similar to that in the past.
My experience has been that you cannot order OOS Online but that once it becomes available... Unless you get the Dreaded "Only Available through the Marketplace" in which case it will not typically become available through B&N during the sale.
Sometimes it can cycle in as little as a few hours. You could check back later. Sometimes in the past Amazon has had pricing close to (or lower) the the 50% price during the B&N sales.
The sale is active (not all prices have been updated as of this writing).
The blurb says " For a limited time, get 50% off select Criterion Blu-rays & DVDs online and in stores now through 8/2!"
Some pre-orders are up eg The Lady Eve on blu-ray or DVD and Marriage Story on DVD but not...