Why would you ever trust a website if you can run a local password generator? Even if it's client-side, that can be changed any moment so why risk it?
Warning: I wouldn't just believe it's the same site on a different domain.
The website is clean. Of course you can't monitor every website you use if it gets changed and what it does over the years (especially if it's a large and complex one), but one needs to grant a little trust, otherwise it would be better not to use the Internet at all.