As long back as i can remember, (started with version 3), the bottom text kerning has always been squished. (technical term)
Just select the text, while still attached to the path, and adjust it with the Shape tool.
Frankly, I'm amazed that you've never experienced this before.
Maybe because we can now stretch the text vertically without distortion, you're noticing it more.
In older versions, if you didn't enlarge the text in proportion, you were sunk. Vertical only stretches were out of the question.
When X3 revamped the fit text to path process, I was in heaven!!!!