It’s extremely common for trainers, especially stand-alone ones, to be flagged as a false positive by anti-virises and security vendors. This has been happening for decades (trainers were first invented in the 1980s), so it’s nothing new.
It gets flagged because of how trainers work, which is by injecting code into your PC’s RAM. WeMod trainers inject the exact same way as FLiNG’s stand-alones.
See more: My antivirus marked WeMod as a Trojan - #2 by Ravenfyre