That's completely false. Hosting a static website on S3 is very well documented.
There have been reports about S3 returning 50x errors, when (as documented) the client should retry. A browser is not an S3 client, so it won't retry ... https://news.ycombinator.com/item?id=4976893 https://news.ycombinator.com/item?id=4977360 https://news.ycombinator.com/item?id=4981482 https://news.ycombinator.com/item?id=2897959