"Yomi <name>" simply means "Phonetic Name."**** They should update the menus to call it that on English systems, then it wouldn't even need an explanation.
But it's not a useless field and it's not just for Japanese. You can use it to help you remember how to say any name that's unusual or difficult to pronounce, which can be very useful for business contacts. (I do use it for Japanese names.)
By the way, this exact feature and implementation has been available in Apple's contact manager since the first iPhone and I don't remember anyone complaining about it. To see it, open the Contacts App, add or edit a contact, scroll down to the bottom,
click the circled + icon for "add field" and whoomp there it is. It even syncs automatically with Outlook 2010 via iTunes.
The only problem I have with this field is that I can only get it to sync with the Windows 8 People App and no other desktop clients, like Windows Mail.