Clock exercise's instructions are insufficient

[a-co]

A student I was mentoring expressed frustration that it is not clear from the instructions that you need to use the CustomStringConvertible protocol to solve this problem. She hadn't encountered CustomStringConvertible before and only found out about it from browsing public solutions to this problem. Is there a pedagogical reason why this information is left out of the instructions? If not, can we update the instructions to include this information so students don't have to look at previous solutions or the tests in order to solve this problem?

Thanks!