Okay I now see how this works. There is no formula evaluation involved in using these types of URLs where for instance the value of _DBID_CUSTOMERS is evaluated to the dbid of the Customers table. Rather the raw string "_DBID_CUSTOMERS" is part of the URL path that is aliased and routed to the Customrs table.
I can see where these types of URL might be of some use in making an application portable when copied in a situation where script was used. But that would largely apply when making API calls. If this style of URL were to ever show up in the address bar or displayed as cover text for a hyperlink it probably will just cause confusion. I think I am going to stick to the practice of parameterizing my scripts with variables prefixed with dbid as they are more readable.
On the other hand if QuickBase uniformly used a URL addressing scheme that included that application dbid and table dbid in all URLs it might provide some nice encapsulation and isolation between applications. For example, such a scheme would allow a Service Worker to register to the scope of an application rather than the overbroad scope of the entire account or the underbroad scope of an individual table (which is the current situation).
One final comment: How in the world did you discover this feature?