A couple of years ago, I went to a seminar on the topic of managing millennials. One point they made has been very helpful for me, and it may be a part of what you're dealing with. This guy could just be a standard know it all jerk, but I figured I'd share.
In previous generations, new hires were willing to put their heads down, work a few years, and were OK with not getting noticed and not making a big impact. They were paying their dues. Eventually they would grow into their career, people would start respecting them, and they may move companies once or twice before they retire. Millenials grew up in a world where their parents were regularly let go due to recession, off-shoring, restructuring, etc. They cannot fathom staying in one company for very long, because they have never seen anyone do it. They need to make an impact quickly, because they won't be around in 3 years. It isn't that they necessarily want to jump from company to company, it is just how they see the world.
Maybe the kid is just trying to show he is useful. His manager should be directing this excitement and drive into something productive.
I am not an engineer so won't comment on that portion of the thread, but depending on the definition, I am on the tail end of being a millennial and can respond to the above. (Born in 85, so just barely in the category)
From the general sense I get from people in this category, it is not that they do not want to be a company man or are unwilling to put in the time to advance at a given company. The issue is there is no incentive to stay at one company because companies today take advantage of long term employees. Look up any thread on the finance subreddits and you will see thousands of replies telling people to job shop every 2-3 years, reason given is that is the only way to advance or to make more money. Most companies will underpay a loyal employee until that employee gets fed up and goes somewhere else, often times while hiring new people at or above the rate of the loyal employee. Gone are the days of being rewarded for being a loyal company man. Better to shop your skills every 2-3 years and take the best offer. Often the old company will come back and try to match it, but by that time it is too late.
Job enjoyment and fulfillment is different for everyone, but feeling like your employer gives a damn goes a long way. At my job I don't make oodles of money, but each year I am given some sort of bump in pay, bonus, perk of some sort. Often times it is rather small, and I could potentially make more elsewhere, but I feel that the employer values me so it is easy to stay and work hard for the company. My wife is 31 and has worked for the same people for 10 years, she is as loyal as they come and works way too hard for those people. She hasn't had a raise in 5 years, got a lousy $15 coffee card for a "Christmas Bonus" and feels incredibly burnt out and undervalued. She makes less than a beginning landscaper but she runs a legal office for two attorneys, one of which almost doubled his income last year, created far more work for her, and gave zero consideration in return. It is quite clear that they will abuse her until she goes elsewhere so that is what she is finally working on. Then they will be royally effed and will be bitching and moaning about how they can't find good help and how no one wants to work hard, because the next person is not going to put up with that BS for long.