Yep, it's worn.

There's no way of knowing why, but lube or weather may be factors. Also, the chain wear rate is highest when using the smallest rear sprockets so that may also factor, though that would need a strong rider to matter.

One other thing to consider is that not all chains are made of the best materials. If this is a low end OEM chain that alone may explain it.

BTW- why would a non-skid surface be a feature on a ruler. Are slippery rulers are such a safety hazard?