Web apps can still have the problem of the server and client getting out of sync.
1. Plenty of people deploy their frontend and their backend separately.
2. Even if frontend and backend are deployed at the same time, there's still the case where the user has the old version of the client loaded in their browser as a new backend gets deployed. I've seen some web apps tackle this by periodically checking if a new version is available and either refreshing the page or prompting the user to refresh the page.
