Its actually not a good analogy at all.
Fastpasses allowed you to go at any point in the day assess the situation, and pull fastpasses for attractions you wanted to go to, when you wanted to go to them. Yes there was an advantage for some going early in the morning, but many fastpasses for headliners were still available at midday and even in the afternoon and evening (particularly in the offseason, but also year round) Some were always gone, TSMM Soarin, etc. But generally speaking you could FP stuff throughout the day, even better, if FPs were gone in a park for attractions you wanted to hit, you could hop to another park and FP stuff there.
Fastpass Plus will require you to book ahead of time, to lock in. The CEO even talked about this in the article linked several times on these threads. The entire POINT of FP+, is to make you lock in. Will there be same day flexibility ? Some, yes no doubt, and more in the off season. But, for headliners and major attractions in the parks ? Good luck if you don't pre-book. There will still be an advantage for those waking up early, they are just going to have to wake up 60 days in advance instead of going to the park early. Those people are still going to "get the jump" on people who take a more casual approach, they are just going to suffer the inflexibility that goes along with locking in 60 days out. If anything this is going to make it so that MORE are gone earlier in the day, and we have already seen some evidence of this, Soar and TT gone before noon in offseason, return times starting at mid to late afternoon on the day, and this is just in the testing phase.
So yea, not the same at all. There is no cyber Monday a few days later with stock still available. FP+ every day is Black Friday, you either prebook 60 days out, or hope to god the stock isn't gone when you show up on the day, and we all know how that works.