[nooop]

By your very own definition, "In theory" means "we have a model that makes good predictions in some circumstances."

If I let "some circumstances" be "non critical use with no attacker" and the model be "very very very very very very very very very very very very very low probability of collision when applied on pre-existing files", I don't see any problem.

The problem is that you were commenting the article using an absurdly geek point of view, interpreting each sentence as it had a very strict mathematical meaning.

In the real world, peoples sometime do misuse the language a little with the resulting sentences being easier to understand for everybody. That is generally not a call for a smart people to point out that when translated word by word (i.e. when poorly translated) using quantifiers, the statement is mathematically false. Especially when everybody on earth understand that use of "in theory" in the first place.

If Jeff wanted to make a mathematical article, he probably had written mathematical statements in the first place.

If every time you see the world "theory" you are feeling you should correct the one using it by telling him about corner cases he very probably already knows about their existence in the first place, you will loose a lot of time for a lot of non-constructive comments.