I will just elaborate a bit about the context because your question is not very informative literally other than urging me to double check the statement.

With request simulation. The program send HTTP request and get HTML from the server. Those HTML is different from the rendered result on browser until the javascript are loaded and executed. To do that, the program need to send request for all javascript, then send everything to a rendering engine. This is very complicated.

With browser automation, the HTTP request will actually get all HTML/javascript/css back and the browser will automatically 'post process' everything, only showing the final HTML to the program. Thus it's a big advantage.