Who cares where they come down
That's not my department,"
says Wernher von Braun
--- Tom Lehrer
Once you learn to count backward to zero.
The oldest manuscripts, namely the Dead Sea Scrolls text of Samuel from the late 1st century BCE, the 1st-century CE historian Josephus, and the major Septuagint manuscripts, all give Goliath's height as "four cubits and a span" (6 feet 9 inches), whereas the Masoretic Text has "six cubits and a span" (9 feet 9 inches). The Septuagint was used for most translations of the Bible until around the time of Martin Luther. Observant Jews hold that the Masoretic Text is identical, to the letter, to the original, but the archeological evidence says otherwise. "The Bible", until recently, measured Goliath as 4 cubits and a span.
During David's lifetime, roughly 1000 BC, the average human male was about 5'6". Hafþór Júlíus Björnsson, who played The Mountain (Gregor Clegane) on Game of Thrones is 6'9", and no one in his right mind would want to get into a fight with him. Four cubits and a span, and ripped, would have been more than enough to cause the level of intimidation described in the Bible. (Oberyn Martell refuses armor, just as David did.)
"Hafþór Júlíus Björnsson, who played The Mountain (Gregor Clegane) on Game of Thrones is 6'9", the same height as Goliath according to the oldest manuscripts of the Bible."
Prisoners were sent there on forced labour, so, as much as I don't know what were they working on, the answer is false/misleading.