Myth 1 is completely false. While companies will be careful about what they have summer interns write, they are absolutely expecting to get real value out of the intern's work. They are spending both money, and the time of the mentor(s) on the intern; do you think they are doing that for charity? Yes, you need to plan for the case that the intern doesn't successfully complete their project; that's why you have things like revision control and code review, to ensure that they don't do more harm than good, and you don't give them a project that absolutely needs to be completed by the end of the summer. Though at most places I've been, there has been more than enough urgent, mission-critical work that the existing developers couldn't possibly finish, so some of it does go to interns as it's not like the existing developers would have gotten to it in that time anyhow. I am mentoring several interns right now, and their code is shipping to customers already, in a core, mission-critical component of our stack.
Myth 2 is something that I'm sure that no one believes. Sure, people try to pick out reasonably scoped and specced projects for interns to work on, just as they do for anyone to work on, but that doesn't mean that they succeed, and I can't imagine that anyone would expect perfection. Furthermore, dealing with ambiguity, changing specs, scope creep, and the like is part of the value of the internship; you're going to have to learn how to deal with that eventually.
Myth 3 is about the only good point of advice here. It is difficult for a mentor to provide enough time for their interns. They usually have a variety of other things to do. But the interns won't be very effective if they sit around stuck waiting for help. Being assertive, and asking for help when you're stuck, will allow you to get a lot more out of an internship than just sitting around waiting for someone to mentor you.
We have three software engineering interns with us (travel startup, 20 employees) this summer from various parts of the country, we shatter most of these myths:
1) All of our interns are shipping live code and pushing to production. We assigned them real projects that our other engineers would have done and pair them with a mentor who has expertise in that area. Our intern standards are that we would hire them today if they weren't in school so they are ready to handle real projects.
2) At a startup, specs and scope are both subject to change without notice but that's the norm so not isolated to interns.
3) We rely on our mentors to find a schedule that works for them but we also throw a lot of team events on the calendar so interns feel like they're a part of the large company.
Many of our full time employees started with us as interns and we often keep them on part-time even after their internships if we really want to them to join us after they graduate.
You can write meaningful, production-ready code if you have the skills.
It seems like you have only worked at large companies, which is fine, but that is likely the core of the "self-fulfilling prophecy" you mention in point #1. If you want to write production code, don't work somewhere that puts 5 levels between you and the deploy scripts.
Where are you interning? Banks? I've "interned" and worked full time at multiple start-ups, there's no difference at that level other than the pay, if you know what you're doing or have a passion to learn it.
Ditto. At a good internship you're not just keeping a seat warm while working on busy work. Working on production code is a fantastic/superior learning experience.
Myth 2 is something that I'm sure that no one believes. Sure, people try to pick out reasonably scoped and specced projects for interns to work on, just as they do for anyone to work on, but that doesn't mean that they succeed, and I can't imagine that anyone would expect perfection. Furthermore, dealing with ambiguity, changing specs, scope creep, and the like is part of the value of the internship; you're going to have to learn how to deal with that eventually.
Myth 3 is about the only good point of advice here. It is difficult for a mentor to provide enough time for their interns. They usually have a variety of other things to do. But the interns won't be very effective if they sit around stuck waiting for help. Being assertive, and asking for help when you're stuck, will allow you to get a lot more out of an internship than just sitting around waiting for someone to mentor you.