Yes.
Our party was our first day. We arrived at 4 pm as allowed and went straight to Guest Relations to get our
DAS (I do not pre-register). How they explained was it will work as normal up until the park closes at 6 pm. Then the DAS tile on the app will disappear. We can still get DAS times but we have to go to the attraction and CM will input manually like the old days. At the time the party starts at 7 pm, the tile will reappear on the app and back to business as usual, for party guests.
It worked exactly like that. We did get a manual time for Pirates so we could ride when it reopened at party time with the
MNSSHP overlay.