The tag would have the advantage of definitively defining a question as a homework-type question. It could also encourage "please-give-me-the-answer" questions, but I actually don't think that that will be a problem in the field of engineering.
What I saw in the process of going through the other communities positions that people linked in the homework questions thread was that they tend to shy away from using tags like homework because they're a meta tag.
This post on SO gives a good description on why meta tags are a bad idea. To summarize, they describe the question itself rather than the content.
Imagine sorting through Engineering.SE by tags. If you look at the questions tagged with civil-engineering, you can reasonably assume that the questions will cover subjects like roads, bridges, buildings, and various infrastructure elements. If you look at questions tagged with homework, it can cover all kinds of subjects. It will provide no useful information about the question itself, except the context in which it's being asked. It won't help anyone with similar issues trying to find it, and it won't do anything to attract more qualified people to answer it.
Ultimately, the fact that it's a homework question is irrelevant, if it's asked properly. The consensus that seems to be developing in the other thread is that we should copy other SE sites' policies which basically say "ask about a specific part of your homework problem, don't ask us to solve the whole thing for you." That helps out the student, the people answering, and the people who will find the question weeks, months, years down the road. At that point, who cares if it's homework? We care what subject matter it is, and that it's a good question. The only issue that arises with homework questions is that I think they're far more susceptible to being done poorly.