The idea that ads affect Google's search ranking just isn't true. There are purposeful barriers between ads and search at Google to prevent this, such that the ads team can't even file bugs with search.
I don't think it would happen at the low level of engineers filing bugs. It happens at the highest levels of management, where the main concern is corporate profits.
Even if there's no explicit cooperation or algorithmic link between the ads and search divisions, everyone on the search management team knows that search is a huge, expensive operation that makes no money on its own. Advertising is what pays for their salaries, bonuses, operating expenses, etc., and you can bet that they make their executive decisions accordingly.
I don't think it would happen at the low level of engineers filing bugs. It happens at the highest levels of management, where the main concern is corporate profits.
Even if there's no explicit cooperation or algorithmic link between the ads and search divisions, everyone on the search management team knows that search is a huge, expensive operation that makes no money on its own. Advertising is what pays for their salaries, bonuses, operating expenses, etc., and you can bet that they make their executive decisions accordingly.