How does "Safely Remove Drive" in nemo differ from eject?

[HyperBear]

It seems "Safely Remove Drive" and the eject command are not exactly the same. For example, "Safely Remove Drive" spins down an external hard drive (not even hdparm -y does this) while eject does not spin down the drive. eject while the drive is not spinning spins it up, even if no partition from that drive is mounted.

Are there any other differences I am unaware of? Is this documented somewhere?

[vanadium]

As I understand, "Eject" merely disconnects the partition. The icon remains, and you can mount later again by clicking the icon.

"Safely remove drive" thoroughly takes the drive "out of view" of the OS. It umounts, but also disconnects the driver, i.e., after that, the system does not anymore see the device. The only way to reconnect is to physically unplug the drive and plug it back in.

[MiZoG]

"Safely Remove Drive" is syncing, unmounting filesystem and powering off device.
"Eject" is meant for devices like optical drives that do not need syncing but it is available for flash drives too which of course as we know need syncing, anyway it is not meant for HDDs/SSDs.
Eject is a standalone program and has its own man page which states that it performs 4 (!) different types of ejection.
"Safely Remove Drive" combines sync with udisks2 commands.

[HyperBear]

As I understand, "Eject" merely disconnects the partition. The icon remains, and you can mount later again by clicking the icon.

No, that's what unmounting does.

After running the eject command, the device is still listed in lsusb and lsblk but with zero bytes in size, and it can not be mounted again without being physically disconnected (or powered on/off if it has a physical switch like some HDDs and USB hubs do).

"Safely remove drive" also unlists it from lsusb and lsblk.

"Safely Remove Drive" is syncing, unmounting filesystem and powering off device.
"Eject" is meant for devices like optical drives that do not need syncing but it is available for flash drives too which of course as we know need syncing, anyway it is not meant for HDDs/SSDs.

So eject on a hard drive or SSD or USB stick does not include syncing?