I would argue that using less of someone's time is strictly "more humane" than using more of someone's time, because an individual's reaction to a situation is... individual
There's no reason an asynchronous coding assignment needs to be more time-intensive than a synchronous coding interview - that's the convention but it's not a necessary one. Lots of companies do 4 hours of technical interviews, it's not hard to come up with an effective programming assignment that takes less time than that.