If that guy was doing the 50T front ring on flat roads, sure. If you pedal at 100rpm, a 50/13 combo at 100rpm is like 30mph. That works fine.
Issue is hilly routes. Going downhill you might go over 40mph which ain't happening on a 50T. Often riding around here the rolling hills I'll hit 45mph downhill on the TT bike. 54/11 combo and spinning out.
Not being able to put out power during that at all is time lost.