Kingdom Heart 3's ending was famously not on the disc and required a day 1 patch iirc.gotta admit, I think it's strange to have things like ramanas park and the island locked behind a day 1 patch. when I was a kid, I was never able to connect my DS to the internet due to our network being WPA, rather than the outdated WEP. if the original games had this, I would never have been able to play the postgame.
I've heard of day 1 patches for bug fixes, but never for major chunks of the game
Another example is Tony Hawk 5 where just the demo was on the disc 99% of the game was downloaded in the day 1 patch.