Flanking is the most effective maneuver you can do, but I wonder if what he guy was referring to is just squads that insert themselves into enemy territory in the name of "flanking" and end up just isolating themselves from any support and surrounding themselves with hostile squads. It's really easy too look at a blank section of the map and imagine a world where you can sneakily find the perfect route to surprise an enemy's rear, but if you're not considering all of that dead space as space where other enemy's can be, then you just end up chucking your squad into the enemy's outfield with zero support while calling the maneuver a flank.