Often times reviews are written by people with English not as a first language, or the reviews are machine translated (nowadays with AI itself). Many AIs use real reviews as templates to train on, so its not surprising to me that the differences aren’t easily spotted. The main tells are when it uses too flowery language and tone and doesn’t get to the point.
To me it seems similar to if you heard an electronic speaker playing a bird call vs. a real bird call, could you tell the real one from a distance?
If you were an expert birdwatcher you could probably tell easier. If the speaker repeated the exact same call on a loop you could tell, if you were in earshot of electronic buzzing in the background you could also, but depending on how sophisticated the speaker is setup (like delay and variety of calls, you might not.