No time is wasted. The bullet train is moving all the time. If there are 30 stations between Beijing and Guangzhou, just stopping and accelerating again at each station will waste both energy and time. A mere 5 min stop per station (elderly passengers cannot be hurried) will result in a total loss of 5 min x 30 stations or 2.5 hours of train journey time!
Factor in slowdown/speedup time and it’s even longer. (thx, nick)