I was assuming when get2sammyb said he resumes from rest mode and provided the time to in-game it is resuming straight into the game like the PS5 first look video shows. So this would look something like turn on console -> select user -> boots to the game's menu instead of turn on console -> select user -> dashboard -> in game (not sure if this was just for demonstration purposes or an actual boot option for PS5). The differences here would be that perhaps the OS takes longer to load everything for the dash (4k dash + things that require internet to load and etc) vs the time it takes to load straight into a game. Included a timestamp from the first look video to show what I mean:
Finally - hereās a sneak peek at the PlayStation 5ās user experience! Watch our new video walkthrough to see new features designed to make your gaming experi...
youtu.be
Notice how he goes straight from the user select screen into the game/control center instead of the PS5's dashboard.
That said it looks like Tom has provided another potential reason for the differences in load time.