It's about the story your application tells rather than "oh, let's give this guy a 0.2 GPA boost to compare him to other applicants because he has an upward trend." Think about your grades and GPA as metrics that they can use to assess whether you can handle medical school. A low overall GPA might be concerning but then when they look at the trend, it might become obvious that you switched career choices halfway through college and so your bad grades were all before you switched. Or perhaps the bad grades were all in your first year because you had trouble adapting but then after that, you overcame that challenge and excelled. These extenuating factors may give them more confidence in your ability to handle medical school and then they may move on to assess the next part of your application.