Scammy would be pretending to be the other brand.

It's the difference between bidding on the keyword BrandX when my company is ABCBrand with an ad that says:

"Come shop at BrandX" .. when it's going to my ABCBrand, and possibly even having a landing page pretending to be BrandX

vs.

"Come shop at ABCBrand" ... and going to my ABCBrand, as it should.