I think it is up to the teachers to provide relevant examples for unit rate problems. If you're not doing unit pricing and miles per gallon problems when you teach unit rates, what are the teachers teaching? The curriculum can't be so specific that it has to tell you what kind of examples to use. Most textbooks I have seen include this type of problem.
It's just like the walkway problem. This is a classic example of a word problem that leads to a quadratic equation. Draw as diagram, label the sides, write the equation, solve it, and throw away the infeasible root. My students can do this one in their sleep.