This was confusing me as well, and i believe OcUK are looking at the same info that i had. Originally a few months back there was only the XG270HU listed - which said at the time it would be 2560 x 1440 TN Film panel with 1ms G2G and 144Hz. no talk of FreeSync.
a month or so later on the roadmap the XG277HU popped up, listing the same thing but with freeSync as a feature. i assumed as well that there might be two versions,. an XG270HU without FreeSync and an XG2770HU with FreeSync. when i queried this with Acer i was informed there was only one XG270HU but it does look like maybe the specs or models numbers got confused.
as i understand it at the moment there is only one XG model, and thats the XG270HU. originally when it was first announced it was not known that it would be freeSync capable. a few days ago i confirmed it was with Acer and updated the news article at
TFTCentral which is where subsequent news articles elsewhere have stemmed from i believe. the XG270HU is a 2560 x 1440 TN Film model with 144Hz, 1ms G2G and FreeSync. it's not expected to be available until mid April, as there's been some delays with FreeSync on the AMD side as i understand it.
The other similarly named model is the XB270HU. That's IPS based with 144Hz refresh rate, and NVIDIA G-sync support. that too isn't expected until mid April