I am far from an expert - but think this is essentially true - but does not universally imply you can't trade on the info.

Example: You watch the front door of an office building. From seeing who walks in, you ascertain with 99% probability that companies X and Y are working on some kind of big deal. If you're just a random person with no relationship to those companies, you can trade on this information.

(Not legal advice! Don't do this unless you are sure it is OK! Which I am not!)