The article is about life insurance, which is very different from medical insurance.
Medical insurance companies often already go out of their way to pay early to save in the long run (e.g. free preventative care, checkups, etc.). I can’t speak to GLP-1s, but it’s possible that right now there are still active patents when used for obesity that make them crazy expensive for a few more years.
Life insurance is all about models and predictions about when you’re going to die. Any sudden change that massively impacts those models suck, because life insurers are basically gamblers with gobs of historical data they use to hedge their bets.