1Password is not autofilling in Safari

So I got 1Password8 autofill in Safari to work if I Allow on an individually website or on Every Website. But the message given when I select every website says "this extension can read and alter webpages you visit and see your browsing history on all websites". Is it only 1Password that is allowed to do this? It makes me worry about a security issue or marketing issue or some-such. Can you explain this a little better for me for some reassurance? Thanks.