It's harsh but it's quite true. Engineers (and other people!) would otherwise have to devote time and effort towards product goals and timeline management -- it

It's harsh but it's quite true. Engineers (and other people!) would otherwise have to devote time and effort towards product goals and timeline management -- it would likely be only half as good as a full-time PM but they'd get it done without trouble. Product managers are an extension of people's normal employee workflows but expanded for coordination and communication, however there's nothing preventing the PM from exercising minimal responsibility on things like product design and whatnot.