Hi neky, the manual update RUU you linked is also "by-the-book" and will give you the exact same update that the OTA update would. It will, however, reset your phone to factory settings, so please back up everything before performing the update.
*The views and opinions expressed on this forum are purely my own. Any product claim, statistic, quote, or other representation about a product or service should be verified with the manufacturer, provider, or party.
RUU is in fact an "official" means of updating the phone. In fact, RUU is a cleaner installation, and less likely to result in random bugs than an over-the-air (OTA) update via the network.
The only downside, is that RUU will wipe the phone of all user data (although anything stored on the virtual SD partition "should" be okay). Backup any personnel data to your computer or cloud solution (and I'd recommend backing up any important data on the virtual SD also, just to be safe).
OTA update is typically not available if you are outside the country where the phone is intended for sale. So RUU is your best bet.