Do you have a mouse plugged in to your computer by any chance?
Same thing is happening to me in Chrome and Safari.
It’s the same issue for the profile page, when you have items that exceed a certain length. Only a portion of the of the preview is visible, yet it has an outer container that’s the actual size of the content, which is what’s causing the excessive white space.
From what I can tell, the intention was to show an expandable preview, which is initially short, then expands as you click on it.
The CSS min-height of one of the containers seem to have something to do with the initial preview being too long.
After unsetting min-height in Chrome Dev Tools
So probably your app is setting the initial min-height based on the actual content instead of the preview.
This bug only appears when “Always” is selected for “Show scrollbars” in System Preferences.