It's not Apple's issue to fix, I don't know what that person is talking about. On macOS the scroll bar is hidden and only shown when you scroll, over the window's content and gets wider if you mouse over it. It has worked this way since 2011 and it's not going to change. There's a setting to disable it system-wide but 1) I'm not going to enable something that permanently takes away 1% of my screen space systemwide just for this 2) this is the default scroll bar behavior, so most macOS users have this issue where clicking the most important "open torrent" button requires waiting a few seconds for the scroll bar to go away.

Transmission needs to add like 20 pixels of padding after the magnifying glass for the scroll bar if the user is on macOS and has this setting enabled.