Their stated goal is to improve the performance of the web request blocking API.
Their (unstated but suspected) goal is to neuter adblocking chrome extensions.
They should have made extensions get auto-disabled if they 'slow down web page loading too much'. Set the threshold for that to be say more than a 20% increase in page load time, but make the threshold decrease with time - eg. 10% in 2023, 5% in 2024, 2% in 2025, to finally 1% in 2026 etc.
Eventually, that would achieve both of Googles goals - since adblockers would be forced to shorten their lists of regex'es, neutering them, and performance would increase at the same time. Extension developers would have a hard time complaining, because critics will always argue they just have bloated inefficient code.