According to the AHCI specification Hot Plug Operation supports both adding and removing devices, see page 88: https://www-ssl.intel.com/content/www/us/en/io/serial-ata/serial-ata-ahci-spec-rev1-3-1.html
Although it is somewhat suggests that it is up to the software (driver) to properly handle it. It seems like the ability to properly eject hot plauugable SATA devices connecetd to internal ports was specifically disabled in the Intel driver for some strange reason. And that part is not clearly documented anywhere.
And it is somewhat missleading that both internal ports and eSATA port have the same "hot pluggable" setting that works differently depending on the port.
Interestingly enough those hot pluggable seetings in BIOS only have effect in Windows and don't have any effect in Linux, all ports return the same list of capabilities regardless of the BIOS settings and any SATA device can be stopped and unplugged. And Windows drivers also implement AHCI support correctly and allow devices to be ejected.
Is there a reason why Intel drivers not fully support AHCI spec?
Thanks.