My vote is for focal points.
First, it's hard to imagine having "stroke thoughts" when you're streamlining off the wall or doing a dolphin dive, but you can have "focal points".
Second, "focal points" seems to me a more accurate description. As I type this, I can see many things: the keyboard on which I am typing, the furniture in the room, a calendar hanging on the wall, a glimpse of the outdoors through my window. But I am focusing on the terminal screen. And that is what I do when I swim mindfully: I am aware of many things, but focus on one.
I also like the idea of having a glossary of abandoned Total Immersion terms. This would help readers to relate old TI material to new material, and would also provide a quick reference on how TI training methods have changed over the years and why.