My chart plotter (low end) gives me a line for where I'm going and where I'll be in 5 or 10 minutes. This time can be changed, but I haven't seen need to. If I were doing 20 knots (BIG if) I'd adjust the zoom level to keep where I'll be in 10 minutes on the screen. If doing 1 knot, I probably wouldn't zoom in - all blue is boring.
In short, I see this thing as a GROSS navigational error. Zoom factor? I don't buy it - this reef isn't an * on a chart - it's 50 km long! Hey, I've hit the occasional * in my time, look at the chart, yep - that's where we're at!