I just closed both browsers, reopened them and still see the difference in fare. Very bizarre.

Carol, Delta is not booking middle seats through the end of June, is also reducing other classes. I am almost wondering if paying the extra $70/pp is even worth it for an assigned seat at this time, but the current seating guidelines only go through the end of June from how it appears.

From Delta:

Giving you more space onboard with new seating policies. Limiting the number of people you pass on the way to your seat and providing you with additional space is a priority. For these reasons, we recently started back-to-front boarding, capped seating at 50 percent in First Class and 60 percent in Main Cabin, and created new seating policies that keep middle seats blocked. On planes without middle seats, we are blocking select aisle and window seats to give you even more peace of mind during your travels. And as you deplane, please take time to create distance for those ahead of you to exit.