I'm not sure if it does or not, but either way it seems like initial page load is the important part. SourceHut is not a single page app, so to compare apples to apples you'd want to load each page individually. Also, it still takes forever to switch between things on Bitbucket after the initial page load. In general for simple things like this with distinct pages, I'm pretty convinced that "single page app" just means that you've made your site infinitely more complicated, more likely to have issues, and more likely to have accessibility problems, for both developers and users for no benefit other than using some trendy new thing.