I haven't personally played I'm on Observation Duty but I have played a similar game called I'm the Caretaker, so my experience comes from that game.
Just in case you watch my playthrough, I want to preface all this by saying that I had no idea this was made in 48 hours lol.
As far as the spot the difference aspect, I think it's great! It's other spots in the game that give me issue. First of all, I think the strike system needs to go away completely. It's already punishing enough having to waste time guessing at a wrong report, the strike system is just excessively punishing.
The strike system wouldn't be as bad if the reporting system was more lenient. I had multiple failures simply because I didn't properly report anomalies because I had no idea what they were classified as. And a few of them were very obvious anomalies so it doesn't feel fair to fail because I don't know what something is classified as. Just let me take my wasted time punishment instead.
Second, this is hardly as relevant given the time frame the game was made in. But there were a few situations where there was a flicker of light or something similar that I'm pretty sure were just visual bugs, but stuff like that in this type of game can be really confusing when you're specifically looking for things that are off.
Lastly, the only truly infuriating thing about the game was the way the cursor controlled. Maybe it was the way it ramped up combined with the sensitivity but it was very tough to click the tiny boxes for reporting anomalies. I'm pretty sure not being able to click the box actually led to me failing once. Basically, it just felt really bad using the cursor.
Sorry for going in so hard on the game, like I said, everything else about it is great! Especially given that it was only made in 48 hours. I only give so much criticism because I find these games to be a ton of fun. Even with the issues listed, I had a great time playing the game. Thanks for making it!