why nuxt prepends `__url` on dev server for client?

if (nuxt.options.dev) {
    const webManifest = `${nuxt.options.app.baseURL}${options.devOptions?.webManifestUrl ?? options.manifestFilename ?? 'manifest.webmanifest'}`
    const devSw = `${nuxt.options.app.baseURL}dev-sw.js?dev-sw`
    nuxt.hooks.hook('vite:serverCreated', (viteServer, { isClient }) => {
        if (isClient) {
          viteServer.middlewares.stack.push({
            route: webManifest,
            // @ts-expect-error just ignore
            handle: (_req, _res, next) => {
              next()
            },
          })
          viteServer.middlewares.stack.push({
            route: devSw,
            // @ts-expect-error just ignore
            handle: (_req, _res, next) => {
              next()
            },
          })
       }
    })
}