'Instant on' isn't a macOS feature. It's a chipset feature, which is extremely clear when you take a look at an M1 MacBook Pro and an Intel MacBook Pro— both, of course, running macOS— resuming from sleep side-by-side. You can see an example here:
It's also mediated substantially by firmware, which is apparent if you examine the resume time of an Intel laptop running Coreboot instead of the chipset manufacturer's original firmware:
Resume from suspend is at about 06:15, and looks like about half as much time (between 1 and 2 seconds) as the Intel MacBook Pro's resume time in the previous video (2-4 seconds).
And strictly speaking, macOS actually turns on kinda slowly compared to other desktop operating systems. It's one of the first things I notice whenever I start spending time on a Mac again! Here's one comparison, for example, on identical hardware:
(And none of that matters relative to what you quoted, because 'sleeping, then hibernating after a bit' is indeed the same behavior, whether your firmware handles the hardware wakeup part of the process quickly or slowly.)
