SLAAC is autonomous. It's more accurate to say that it tells a host to assign itself an address, rather than that it assigns an address to the host.

No, SLAAC is the name of the configuration mechanism, the network protocol that is used for SLAAC is NDP, specifically router advertisements (RA), and SLAAC assigns a specific address to a host, based on the information in the RA and local policy on the host that specifies how specifically to generate the host part of that specific address.

...you seem to have just copied and pasted the post I replied to.