Answer: They aren't. The article doesn't mention a single instance of anyone actually ingesting borax, just "some TikTok users are encouraging viewers to add borax to their water"
The thing is that borax (a boron compound) is a cumulative poison.
Keep up adding that boron to your water over a lengthy period and it's curtains. There is a reason that borax is used to kill ants and other creepie-crawlies.