Twitter viewer tools are a crowded category, and most of them are small projects with a single developer. That means a short history and a missing About page are common, not alarming. The real question for twitterwebviewer.com is whether it behaves like a tool you can rely on.
The evidence points to a functioning site with real traffic, and the technical side looks maintained. But the operator hasn't made themselves easy to find, and there's no confirmed privacy policy from our check. For a tool that might see the Twitter URLs you paste into it, that's a fair reason to be cautious.
Is twitterwebviewer.com a scam? Nothing in the available checks says so. It's more accurate to call it unproven. If you want to try it, use it for public posts, avoid connecting any account, and stop if it starts asking for permissions or personal information that a viewer shouldn't need.