The expose male connector is OK; it's not a double-ended male cord, and there is no chance of the terminals becoming energized.
I don't see references to any listing agency on their website, though. If it's not listed my an agency the AHJ recognizes, it's not legal.
I don't believe it's an extension cord, though, because extension cords are by definition temporary. This appears to be permanant building wiring. No different than a hardwired pass-through for a portable generator. Honestly, I was thinking about doing something along these lines in my own home because I didn't feel like tearing up the drywall to try to drill 2 studs over to hit the nearest box.
Edit: They claim UL and CSA approval:
Federal Specification UL # WC596
U.S. UL File # E140596
U.S. UL File # E146159
Canadian CSA # 1765
Canadian CSA and CUL reference to U.S. UL C22.2 No. 42