ABP released a statement to german news site golem.de, saying that they "prepare for the worst case".

This means they anticipate Google to target the Acceptable Ads program.

Originally I thought 30,000 rules wouldn't be enough to cover things, but according to this research, only a couple hundred rules are enough to block >90% of the ads: https://brave.com/the-mounting-cost-of-stale-ad-blocking-rul...

So maybe there's another limiting aspect of the declarativeNetRequest API I don't know of.