This propagation delay does not really matter as long as neighboring power plants are synchronized with each other.
Yes, east coast and west coast are out of phase, but only to a perfect observer who can see phase value on both coasts instantly (without a propagation delay). However in reality information about the phase cannot travel faster than speed of light, so to any real observer anywhere between east and west coasts both sides appear to be in sync.
I believe this comment is not directed to people who are trying to create something, but to people who feel entitled/special because they are trying to create something they perceive as improvement for humanity.