How is "most of that pressure gone"? You're still being evaluated and have to code against a clock, with less time, less opportunities to ask questions and less immediate feedback that could get you back on track.
Also, your 20 vs 30 minute calculation ignores that companies are incentivized to conduct more screening tests if it becomes practically free for them. But the number of positions stays the same. So if instead of 10 screening calls they do 16 tests for one position, that's already more time being wasted, even if the tests are 1/3 shorter. And realistically, the number will shoot up much more.
Also, your 20 vs 30 minute calculation ignores that companies are incentivized to conduct more screening tests if it becomes practically free for them. But the number of positions stays the same. So if instead of 10 screening calls they do 16 tests for one position, that's already more time being wasted, even if the tests are 1/3 shorter. And realistically, the number will shoot up much more.