Having the actual url be completely different from the displayed url simply shouldn't be possible. Allowing that invites scams like these. At the very least, they need to be the same domain.
the g, i, m, or p are replaced with characters from a different character set. Looks right, but the domain is registered with a different character.
Example: * gіmp.com is fake. * gimp.com is real.
They look the same, don't they? But if you click on the fake gіmp.com, your browser will take you to the domain xn--gmp-jhd.com as it is using the і from the Cyrillic character set.
(Mostly I mention this because someone else might be thinking at as well.)
They might work for BigCo, but rather than have the ad point to bigco.com/product they instead have the ad point to tinyurl/bitly so they can track how many people click the ad and repoint it to another URL easily.
There is a whole industry of these redirection services that gather stats, direct users different directions based on mobile/desktop or country. It isn't rare to bounce a user via a whole chain of them.
To support all those users, ad networks have to allow the apparent URL and actual link target to differ.