Usage is floating and amenable to change. At some point usage was different from what you claim it is now (do you have sources to back that up, btw?). The "small fact" people sure didn't let 'em stop that from using the word wrongly (at that point of time, at least, "small fact" was wrong according to your definition, also).

Edit: I checked the Merriam-Webster, and there at least the classic definition is listed as the primary meaning. The alleged "current use" is listed as secondary. I think we can agree your claim to be a factoid - we just can't agree on what that means! :)