Well, it depends. Sometimes such titles are used a bit loosely. While there might be a kernel of truth, the story could be highly dramatized. In the case of something related to Jason Bateman, it could be based on a real event in his life or something he was associated with, but it's also possible that it's just a marketing ploy to draw in audiences who are interested in 'true stories'.
Yes, often when something is titled 'Based on a True Story', it implies that it has elements rooted in real - life events. However, it may also take creative liberties for the sake of entertainment.
In many cases, when a production is named 'Based on a True Story', there is some truth to it. For example, if it's about Jason Bateman, it could be inspired by an actual incident in his acting career, like a particular project he worked on where the general premise was based on real - life happenings. But it's also common for filmmakers to blend facts with fictional elements to make the story more engaging. Maybe it's about his early days in Hollywood, or an experience he had on set that has been adapted into a more elaborate narrative for the screen.