App stores are taking 30% off the top. The article doesn't talk about that, so I wonder if they are taking the total and working from there.
$1000 in donations means $300 to the app store, which would leave $400 for TikTok and $300 for the streamer. While that still doesn't look as good, 40% is significantly less than 70%.
Edit: In the test they performed, it's clear they are ignoring the app store fee. Simply put, this is a really misinformed article at best.