Well, it turns out it was real. I've posted Gweilo8888's comment below.
...The "Good World Hotel" is listed in a 1951 Chinese-language book indexed by Google as being at "62 Wan Chai Rd".
The same name also appears in the 1964-65 Hong Kong Trade Directory as being in Wan Chai, and although the formatting of the text snippet is wonky, it seems to list them at "62-78 Wan Chai Road".
Looking at Centamap, there's a "62-76 Wan Chai Road", which is now the somewhat bizarrely-named Fully Building, occupied 12/1981. So my guess is that the Good World Hotel is a real place in Wan Chai, and was demolished for construction of the Fully Building about 5-6 years or so after Shatter was filmed.I can't match the background either which leads me to think that the hotel entrance was slightly further up the street and opposite a new building (called "83Wanchai") that stands at 77 - 83 Wanchai Road.
The buildings across the street date back to 1951-1967, incidentally, so the view out the door in frame grab 16 should match one of them, although I really can't make out much in it myself.