This is an Electron app, meaning it does not look, feel, or perform like a native Mac app. FYI in case that's important to you.
$ rm gitkraken-amd64.debTry opening a large repo and scrolling a list of commits in GitKraken. You'll see large blank areas that get filled in after a few seconds. Now try it in, say, GitUp, which uses NSTableView: it is perfectly smooth.
Having nothing good for long lists doesn't matter as rendering pipline on OSX didn't updated for a years. Almost everything in UI on OSX is still software rendered instead of GPU. And Chrome extensively use GPU for rendering and that outperforms everything.