I have no proof but I really think this is going to be another one of those pop-science "facts" that is eventually proven false. One of those ones like "playing classical music makes plants grow faster", it just doesn't sound right.
The headline implies something that would be misleading if you don't know how strength works. It's not about increasing the abilities of your muscles, it's motor learning or the ability to use your muscles. Your strength isn't just what your muscles are physically capable of doing. It's also your ability to use those muscles. You need to train your brain and motor pathways how to optimally use them. This is the mind body problem or mind body connection: https://en.wikipedia.org/wiki/Mind%E2%80%93body_problem
My personal anecdote is that this is quite effective. Anyone trying to lift heavy weight is going to psych themselves up beforehand. Part of that is thinking about the lift, how they'll do it, and how they'll succeed. It definitely helps.
I've for example been lying in bed before with cold toes and by focusing on heating them up in my mind I swear my blood circulation improves much faster than if I don't.
Just anecdotal of course, but considering the role the brain plays in the body I don't see it too far fetched that it can to some extent influence either of the above.
It's feasible to me that thinking/visualizing a motion could improve your ability to recruit those muscles