Another website url as an anchor leading to a website

How does it impact the SEO of the website if there are anchors with other website url leading to it? For example, the website name is 123.com but the anchor url leafing to it is 456.com.

That's how it is suppose to be. It looks non-spammy that way. Just add more anchored texts to your targeted site.

Isn't it confusing? You click on a url with the anchor 456.com and you end up on 123.com? I know Google bots are not human but don't they disregard such a method?

It can confuse both users and search engines about the relevancy and context of the link. If there's a legit reason (like a rebranding or merger), make sure to have consistent, relevant content on both ends. Otherwise, it's better to use brand-appropriate or keyword-rich anchors for clarity. This avoids any potential red flags for search engines and helps in maintaining a clean link profile.