I don't know about this MLS coach, but Marcelo Bielsa runs a man marking system. If you don't win the back back quickly high up the pitch, you can easily ship goals in bunches. See: Leeds when they first made it back into the premier league. His last full season at Leeds saw them give up >2 goals per game for the season. It's exciting to watch, but it's hard to win at the top level that way.
In this article, Jon Mackenzie covers the four basic principles of Marcelo Bielsa’s defensive system as it has appeared at Leeds United…
allstatsarentwe.medium.com
Other coaches will selectively man mark in the counterpress, just to choke off options for the player with the ball, but it's not necessarily all over the pitch.