And you based that point on unity's licence being per seat, implying that they don't have a profit incentive to push for IAP/ads.

Their point was that this implication isn't correct, because unity does indeed have a profit incentive for ads and IAP, as they're providing a platform for such. It's one of the features unity mentions on the pricing page.

What do you think the IAP incentive is for Unity? It's just one of the cross platform features they wrap. It's surfaced on the pricing page because it sells the engine but there's no monetary incentive to Unity if you use it or not.

Unity takes a cut from its ads business but it just does not do that for IAP any more than the animation system.

So fundamentally, ad prices in the mobile game ecosystem are driven by life time value. IAP is the biggest contributer to LTV, this Unity care about this. I'd like to know which portion of their revenue is bigger, but I can guarantee that the ads business is growing faster.