Based on my experience with previous Pis, I bet you’ll be able to drop that even further by turning off unused board components at boot time.
# Disable Power LED after boot
dtparam=pwr_led_activelow=off
# Disable SD card activity led
dtparam=act_led_trigger=none
dtparam=act_led_activelow=off
# Disable the ethernet LEDs - these are Pi4 specific values.
# Look in the docs for the values for other Pi boards.
dtparam=eth_led0=4
dtparam=eth_led1=4
It appears to depend on firmware or kernel but for recent kernels (recent 6.1 or 6.2) activelow is no longer necessary [1]. It seems to work on CM4.
The required lines were different between the Pi 2 and Pi 4 I was using at the time, and the documentation was not updated (or I'd found old docs).
An exercise in trial and error.
The same likely can be built on top of an RPi, using, say, wake-on-LAN signaling, or some GPIO as an interrupt source. You'll have to suspend your OS while idle for a prolonged time though.
My reading of that was:
"soft" = trigger an orderly OS shutdown, the same as if you executed `shutdown now` on the command line.
"hard" = cut power immediately, as if you just unplugged the power cable.
I dream of DIY'ing a laptop, and RPi looks like a great platform for prototyping that... until you realize there's just no sensible way to put it to sleep. Hibernate + aggressive boot time optimization?
Eventually though it didn't turn out to be much of an issue, SSDs boot real fast these days anyway and I can just do a full power cycle.
The real unanswered question is, does it finally have a damn sleep mode so it can save power when idle.