Yes, if every single URL in your web application has a hash in it (including <a> hrefs) then you don’t have to worry about anyone maliciously serving a webpage

Yes, if every single URL in your web application has a hash in it (including <a> hrefs) then you don’t have to worry about anyone maliciously serving a webpage anymore. But how do you get new app versions? I argue, if you want any meaningful security guarantees, an answer to this question will require transparency and/or code signing (which itself requires transparency, per my comment below)