If I remember correctly, these are profiles in the same sense this term is used in Firefox - i.e. a global setting that can be switched, but applies to all active browser windows at the time. So you can't use it to (easily) browse different websites in different profiles side by side.

In Safari, "profiles" are a per-window thing, and there are facilities to open a website in a different profile etc, so effectively they work much more like Firefox containers (which are even more fine-grained tho: per-tab).