Some sources will make a distinction between those two terms. Many will use them interchangeably. You can't assume that the word choice means something one way or the other unless you know the person writing it makes that distinction.

It's the same as the sportcoat/blazer issue. Sometimes people use "sportcoat" more often for a hunting-inspired jacket, especially if it's tweed. A "blazer" is more likely to be nautical-inspired and might have brass buttons. But just because a jacket is described by one term rather than the other, that doesn't necessarily tell you anything.

There's also the famous shoe terminology issue. Sometimes an "oxford" is a shoe with closed lacing, while a "derby" or "blucher" is one with open lacing. Other times, an "oxford" is any lace-up dress shoe, and only the name "balmoral" specifies closed lacing. And then, sometimes "derby" and "blucher" are used as synonyms, but occasionally they refer to different styles.

These are all just terminology differences. There's no sense getting worked up over them.

This is the first time I've heard of a khaki/chino distinction, so I'd normally assume the words are being used as synonyms unless I know the writer means to draw a distinction. However, it is good to keep in mind that, whatever you call them, sometimes they are more or less formal due to various details like seams, the presence of a crease in front, how thick or rough the fabric is, etc.