It's very much real, you cannot tell the difference between an upset and a fixed game, they will try to make it real because there's a big risk for them if they are caught.
If you're on the expert level of analysis for the sport that you love and are a fan of. You'll be able somehow to spot on which is a true upset and likely a thrown and sold game.
But it's true that there's difficulty in finding which of them are actually thrown because when there are fixed matches, they're likely not to do obvious things that will destroy and spot it by their fans.
Especially when you take into account that there were so blatantly obvious thrown games in the past that they now try to become more sophisticated in fixing games. I guess there is no doubt that there is still fixing going on, but there is such a vast majority of betting options these days that I believe that even plays into the hands of scammers. Fixing a game with an own goal or a penalty is really obvious, but what about a defender's mistake to kick the ball to a corner during the first five while pretending to just technically mess up. Sure it could still be suspicious, but as it might not be decisive for the game there will also be less scrutiny.
Yeah, you can't just ignore obvious moves that shouldn't be done. You'll find it suspicious if you're going to watch that afterward and analyze the game.
You can really spot them on and can't ignore the fact that this should be done like that or this. You'll have that realization that there's something wrong if you go through and observe the game again.