1 : an invented fact believed to be true because it appears in print 2 : a briefly stated and usually trivial fact

https://www.merriam-webster.com/dictionary/factoid

It's often used for a "trivial or minor fact" but by comparison with planetoid (something like a planet but not a planet) or cuboid (like a cube but not an actual cube) or asteroid (looks like a star but is not a star) or humanoid / android (having the form of a human or man while not actually being one), you can see what the 'correct' usage should be.

Trivial fact would perhaps be better as 'factette' or 'microfact'.

If I choose to label them "incorrect" for their usage of "factoid", by your own argument I'm absolutely right.

Descriptivists may say yes, but that doesn’t mean people won’t try to stop the meaning drifting to prevent the past becoming inaccessible.

Seems to have happened with "momentarily". Used to mean "for a moment" but now most people use it to mean "in a moment".

I remember being amused the first time a flight attendant said "we'll be taking off momentarily".

It depends which people you are talking to.