Not as Apple.com states.
Use context clues, you have to read the whole paragraph:
"If you buy iPhone for T-Mobile, it will arrive with a nano-SIM card already installed that you can activate by visiting an Apple Retail Store or a T-Mobile store or by calling T-Mobile. [ONLY] When you travel internationally, you can use a nano-SIM card for iPhone 5s from a local GSM carrier."
National carrier, T-Mobile.
International carrier, local carriers.
Sounds like locked nationally, unlocked internationally, which is a common one.
In which case, you will, again, have to contact T-Mobile to unlock your phone for international use.