Specifically something which seems simpler than an alternative at first glance but is actually complex on a closer examination.
There are some things that have been coming up at work that fit this description, but I feel like if I had a good word or term for the phenomenon people would better heed my warnings.
Edit: My particular situation is in software development, but isn't exactly scope creep or over-engineering. I'm not at liberty to provide a detailed example, of which there have been several, but the one that motivated this post is the selection of a tool. The tool that a coworker has recommended has a very simple interface. The fallacy that I'm trying to describe is that the tool will make easy tasks easier at the expense of making harder tasks harder.
Edit 2: A better example (for the software engineers, anyways) would be duck-typing like in Python. At first glance, it should make things easier, you don't need to declare a type for every parameter and variable. In large projects (IMHO) this adds complication because its harder to track which parameters expect which data types.