He isn't referring to a single level, he's talking about Half Life 2 overall, and there is a lot of explosive barrels throughout, excluding that one underground area filled with explosives and Manhacks because those are used against the player rather than the enemies
I'll say that i like and had fun with Half Life 2, but i also get what Tony's saying about the difficulty
The hardest thing in Half Life 2, IMO, was the Strider battle at the end of Episode Two, and that's because you have to multi-task between Hunters, Striders, bases, refuel on Magnusson Devices, rockets, AR2 alt fires, etc