I was speaking about Shanghai Disneyland, not DLR in California. They said on the call yesterday that what they do for Shanghai may not be what they do for domestic parks. I'm not sure if the poster I responded to is traveling to DLR or WDW, but I was mainly addressing her concern that when you purchase your tickets matters - I didn't get the impression from the call that it does.
I just mentioned WDW because I know their tickets are currently set-up in a sort of date-based way since they implemented the date-specific pricing structure. You at least have to choose a starting date for your multi-day WDW tickets, and then there is a window of time (based on ticket length) that you can use those tickets on and after the starting date. I am not familiar with Disneyland's ticketing structure so I just mentioned what I knew.
Of course, no one knows as of yet if that will still be WDW's system when they reopen the domestic parks. I have seen mention on the boards of Disneyland's Flex Pass reservation system, so possibly that sort of system will apply to multi-day tickets that aren't purchased for specific dates, like the situation you describe. People who purchased WDW tickets back under the multi-day, no-expiration-option system would also fall into that sort of situation. I am sure they will address all of these scenarios and provide some kind of solution when they have a game plan ready, though.