"You can use camera expressions anywhere an expression may be used." is incorrect and meaningless.

In the docs, it says:

You can use camera expressions anywhere an expression may be used. When you use a camera expression as the value of a layout or paint property, it must be in one of the following forms:
...
That is, in layout or paint properties, ["zoom"] may appear only as the input to an outer interpolate or step expression, or such an expression within a let expression.

The first sentence basically doesn't mean anything that is true. The second sentence so drastically qualifies it as to make it essentially meaningless. IMHO it should be removed.

It would be more straightforward and correct to remove both the first two sentences and simply write:

In layout or paint properties, ["zoom"] may appear only as the input to an outer interpolate or step expression, or such an expression within a let expression.

Locate the documentation section containing the quoted camera expressions text and review the linked interpolate, step, and let references. Remove the two criticized sentences and retain the proposed direct wording about where ["zoom"] may appear; done means the documentation is concise and accurately states the restriction.