b) Not really. Whether "Shot with iPhone", or DSLR pics cropped to the phone screen, they both imply to Ms Average that they could take their phone out of their purse and achieve the same results. Otherwise why bother with campaigns like that? Unless Ms Average has a bunch of slave flashes and lenses in there too it cynically misrepresents. A simple tripod or monopod mount would be OK, as that still fairly represents "what's in the box".
Like the GP noted, phone cameras are surprisingly good within their well known limitations. They could achieve perfectly good, but honest, advertising photos just by staying within those limits. They would just never achieve the results an SLR with large, fast prime lens, and large sensor, or even arrays of additional equipment plus phone could.
A vague disclaimer does not, and should not, replace honesty and presenting what's "in the box".
b) there is a categorical difference between using a different camera and presenting it as if it came from the phone and using external equipment to supplement the phone.