I am not going to comment on whether this is a scam project or not as I don't have enough information about it. However, I want to comment on this point:
they claim to have agreed to list on Mexc by 10th May, but no info from Mexc.
This is not correct. MEXC announced on one of their tweet they will list STN token soon although they didn't provide an exact date:
MEXC is thrilled to announce that $STN will be listing soon!
...
As I said, I just wanted to correct the above point and not saying the project is legit or anything like that. DYOR before investing!