My use case is that I'm scrolling and I get bored with a thread. It isn't much different to swipe up on the thread to scroll down further if I wanted to keep reading, and there is no easy way to just jump to the next top-level thread. I'm left either having to collapse several levels of comments to condense things, or scroll until I hope I find the next one and don't miss it.

At the very least, I feel like this should be configurable behavior for the button.

But again, this is just me, so you might have data saying people want otherwise, and this is free so I shouldn't complain :)