There is definitely truth to this and I don’t think this is contrary to the other posts here at all.
It is just about finding the right time to move on. If you don’t yet have enough experience and accomplishments at your current place of work, it’ll be difficult to move up somewhere else.
My assumption is that it would probably take more than a year in one job to actually learn the ropes, take on more responsibility and to start to own projects. Especially at a reputable firm.
Unless the working conditions are unacceptable, you should have substantially more to show after you leave than when you started.