the ones in North Africa, such as t.g.gracae, Libyan and Tunisia, don't need hibernation, they need always be in a warm dry environment.
Other Greeks in north area, like t.g Iberia, need hibernation definitely.
The Middle East ones, including many golden ones, are said to need only a short time hibernation or none. I am not quite sure, and will read more material.
Whether or not your captive Greek tortoise's specific species (or subspecies) brumates (hibernates) in the wild depends solely on the region that it or it's parents originated from. Generally those found in North Africa and much of the Middle East do not truly brumate. However, depending upon their wild population location, some may become inactive (but remain awake) during colder than normal weather and many in warmer climates will aestivate during extremely hot and dry weather. Northern Ibera Greeks do brumate and for long periods of time, as long as 6-7 months in many areas. Ibera found throughout Turkey and far west and south may also brumate, but for a much shorter period of time.
In captivity, if you are unsure of the species or subspecies that you have it is always safe to not brumate them. None of them truly need to brumate in captivity.