Earlier quoted context omitted.
Even ROI can't be counted separately, as both companies can count the same conversion as theirs (up to 30 or 90 days layer if I recall correctly). You really need to use 3rd party for validation.
And then you can't do viewthrough (especially on mobile). It's a mess, to be honest.
Basically saying a non-guaranteed second of eyeball time in a banner-blind spot from someone they're retargeting who's already visited our site who converted 60 days later is their acquisition. [0]
I'm a marketer and I despise some of the crap these ad companies are selling.
[0] Conversely, this makes my personal KPIs look amazing, since I can take credit for other people's work and attribute it as my own. Obviously not doing that has caused me twice as much work to get proper attribution set up. If you want an easy life, push the BS metrics they give you.