for me it was the article's title

Watching it at a relatively low bitrate on my phone the two things that stand out are the drinking glass and the lamp. The glass is too perfect - a real glass will have tiny deviations in wall thickness and surface imperfections that are apparent when you look through it, especially when moving around, glasses are always one of the biggest giveaways for me.

The lamp also has something strange going on and doesn't look like any real diffuser. I think they've tried to use surface roughness to simulate frosted glass, but have made it too translucent. It doesn't look like a translucent plastic either because of the high IoR, and have possibly made it solid rather than walled.

Rewatching it trying not to pick out too much is difficult, but if I would add one more thing it would be the very uniformly rainy windows which have some gridding to the droplets (and the small error of putting the shader on both panes of the doube glazing :p)

The perfect camera autofocus when object distance changed quickly, especially since it's "macro" distance at times. No real camera auto focus is that good.

Also, some things are too perfect/lacking imperfections. The lamp shade texture for instance is too even & perfect

I think I was primed because of the title, so I was more attentive. For me it was the candle that appears unnatural, also pencils are a little too perfect and the label on the lighter is a little too clean. After 10th watching also the speaker and the wooden thing look a little artificial. If I didn't know it was a render I might have put the oddness of the candle on some compression issue.

Not "giving away", the lighter and pen certainly are captivating, but more like on a second view some things clearly stand out as CGI.

1. The window. The water behavior is straight impossible, I think. Too much water an the glass.

2. The lighting dynamics and lens distortion are slightly off in this uncanny valley way. Too algorithmic, too smooth.

3. Clearly the lighter and pen have gotten the most touch up. Everything else is a bit too generic. Additive and subtractive manufacturing leaves marks and uneven deposition.

In reality, sometimes things do look weird from a certain angle, and they never avoid the impression of CGI origin, ironically. It's really hard to perceive and recreate the world the way it is, because your brain only ever constructs it as mix of filtered and processed visual input and internal modelling. Very well illustrated with the involuntary multi-stable perception phenomenon [1] and illusory contours [2]. People are blind to the way things don't look like the things they are. I think, artistic mastery is overcoming the inherent limitations of perception and becoming fluent and expressive in the unspoken language of pre-cognitive expectations, symbolism and archetypes.

[1] https://en.wikipedia.org/wiki/Multistable_perception [2] https://en.wikipedia.org/wiki/Illusory_contours