Texting while driving is actually a desirable skill for military pilots. They specifically look for people who can drive a vehicle while holding a conversation and monitoring several screens. Being chased by a lion would certainly focus the parts of the brain covering perception, balance and coordination. And learning to control one's panic responce is essential cognitive development imho. My point is that essentially any complex activity is a learning experience, a time of increased brain activity.
The article and study is not about learning though, it is specifically about memory. I doubt anyone would claim that learning to drive was best done by taking notes at a lecture (texting or otherwise), as it is about training reflexes and habits, essentially so you can do it without thinking. Because thinking is slow. But maybe the best way to to learn Latin irregular verbs is to scream them out while being chased by a lion; that would require further study.
Somewhat related, I recall a study on how we find it easier to perform complex mechanical tasks while moving our tongues or sticking them out. Which seems to be how our brains use of language gets tied to physical activity when we need to really concentrate and engage higher thought. I can grasp how writing could well improve memory formation, forcing us to codify thought into language, engaging those parts of the brain that use language for reasoning. But interesting if typing does it worse.
