I wonder if you've misread the article. Keeping a perfect continent-wide 60 Hz. as a 'timing pulse' is very 1950s. Anything that relies on it now is bad technology. IIRC, it takes large base-load plants to manage frequency corrections. If we want a more flexible grid, with multiple inputs from solar/wind/tidal plus fire-on-demand natural gas plants, allowing a small range of deviation is practical and desirable.

My 2c.