My guess is that this is part of a push by Disney to get everyone to go to the parks early. 7 AM for this (and boarding groups) as well as the 30 minutes early at every park.
I much preferred when the parks were open until 11-12 at night (and not via an extra ticketed event). But I think Disney is trying to get guests to show up right at park opening and then be happy to leave at 8 or 9 to make operations easier for them, as well as reserving all the later hours for the deluxe resort perks and extra revenue events.
I don't think Disney wants anymore people showing up right at opening. I think Disney would rather have 2 groups of arrivals. The group that rope drops, but heads out to get dinner somewhere else. A 2nd group that shows up later, but then stays in park for dinner and closing. The less literal version of "selling the park twice."
The biggest thing preventing more people from doing this is that guests know if they arrive late, there will be too many lines to guarantee that they can get everything done that they want. Everything Disney has done recently is to try to figure out how to change this dynamic. More nighttime entertainment, FP+, After Hours, and now LL. FP+ gave people the option to arrive early or late depending on how they arranged their FP+. I hate the system, but we did use it to avoid rope drop as my Dad and I got older. But, I suspect people who want to be more casual about their arrival times also want to be casual about other things... like booking windows. They weren't scheduling FP+ that far in advance, and certainly weren't waking up in the middle of the night to book their 60+ FP+ and thus a set of specific rides were unavailable which forced people back into arriving earlier to give themselves enough time to get everything done that they wanted. Instead the commando group of "why not both?" prided themselves on their ride stacking capabilities and took midday naps and pool time and declared it the best thing ever, which for them, it probably was, but it didn't "sell the park twice."
With LL, Disney hopes that potential late arrivals can wake up at 9 or whenever, casually schedule their first attraction from their room / home, maintain LL availability within a 2 hr return when they actually arrive, and sustain this into evening hours. And they can use price and LL/standby ratio as dials to achieve this. Making late arrival a viable option. For week 1, unless you want Rise or SDD this is working out*. The small sub-set of late arrival commando optimizers are driving themselves nuts over 7AM, but Disney needs to offer it for the rope droppers. To quote Jack Sparrow, "This bullet wasn't meant for you."
The elephant in the room is that demand still outstrips capacity for E-ticket headliners. Eventually Disney will not be able to manipulate the ratio without hurting standby or avoid early sellouts or the price would need to increase so high that those start becoming deterrents to the late arrival option again (why arrive late when Genie+ costs so much). Even people with money would rather just have an After Hours event. No matter what people think it will do, insufficient E-ticket capacity is driving how people plan their day, and will continue to do so unless there is more of it (higher capacity E-tickets) or gives people other options (I don't need to ride SDMT because I would rather ride X). Given the problem child rides, the thing Disney needs the most of are high capacity, slightly thrilling without being extreme making them still family friendly, themed attractions. Those don't come cheap.
* Test Track and Smuggler's being the next in line for this not working out
