That seems a somewhat contrived example. Yes, it can theoretically happen - but in practice it would happen with a library, and most libraries are LGPL (or more permissive) anyway. By contrast, there have been plenty of stories lately of people who wrote MIT/BSD software, and then got upset when companies just took the code to add in their products, without offering much support in return.
Also, there’s a certain irony in saying what essentially amounts to, “Please license your code more permissively, because I want to license mine more restrictively”.
Not exactly. For example, you can’t make the whole thing, GPL snippet included, available under MIT. You can only license your own contribution however you want (in addition to GPL).