I read on some newspaper article about this ominous 757
Nothing ominous, but the 757 is normally classified as a Heavy, despite it being under the 136,000kg limit.
Here's the excerpt from the Australian AIP:
Note: B757 and H47 (Chinook) are categorised Heavy (H) when the following aircraft is categorised either Medium (M) or Light (L) and categorised Medium(M) when the preceding aircraft is categorised Heavy (H).