The way named workspaces are generally used makes them more "attached" to their
original output.
For example, you have a two-monitor setup with named workspaces on both. When
you disconnect the monitor to go somewhere and work for a while, then return,
you probably want your named workspaces to return to where they were on your
second monitor.
This is in contrast to unnamed workspaces which are more transient and should
more easily follow you wherever you're working.
Ivan Molodetskikh