I'm not sure what it means other than "MSFT isn't really paying attention to making sure W11 works well on HDD boot drives".
Does it mean extreme inefficiency with disk access, or does it mean heavy read-aheads plus aggressive caching? Who knows, but if you Google for "Windows 11 SSD optimized" you'll get pages and pages of results about SSD bugs and issues that have plagued large swath of users. Eg. KB5007262
In games, for example, games that are designed around HDDs might pack 3 copies of the same tree so that I can be loaded at the same time as other assets in the scene with limited seek time and decompression time. SSDs, having no seek time, don’t need elements to be in adjacent locations.
Granted that is for video games, but to develop for hardware is always at the expense of every other hardware
With ssd and nvme drives being available for cheap, it's probably not worth devoting engineering resources to improve it. They still cater heavily to OEMs and many of those have stopped specing spinning disks for the boot drive.
Does it mean extreme inefficiency with disk access, or does it mean heavy read-aheads plus aggressive caching? Who knows, but if you Google for "Windows 11 SSD optimized" you'll get pages and pages of results about SSD bugs and issues that have plagued large swath of users. Eg. KB5007262