1) more demand in auctions means higher prices. so if apple is taking the second slot they’re almost certainly increasing the cost of the 1st slot for hbo. which is apples whole point: to increase the cost (literal and figurative) of hbo’s efforts to get people to sign up via web rather than via app.

2) in the world of search marketing - including both on google and the app store - there is a strong belief by brands that they MUST be the #1 paid result for their branded search terms, no matter what. so what you’re seeing here is hbo saying “we always have to be #1 on our branded search no matter the cost”. This is exactly why people complain constantly about google showing competitors ads when the original company’s brand is specifically searched for by the user - effectively the competitor is freeloading on the incumbents brand searches to drive traffic (by paying to show ads on those searches). Google doesn’t care because they make more money this way (more competition for the branded keyword drives up CPCs).

all of this is to say that apple being in the #2 slot doesn’t say anything about the intent of their actions here, which is to make it uneconomical for companies to move users off apples rails onto their own systems.