When a template subscribes to data in a server collection, there is a delay between the moment the subscription begins and the moment the client displays the data it receives from the server. On page load you really notice the delay because there is nothing else for the user to see while the client waits to receive the data from the publish action. The way around this is to show something else on the page so that the user doesn't notice the delay. One way to do that is to show only static assets during that time, another way is to use local (client-only) collections.