I also only know of bruschetta as an appetizer of bread+topping.

Bruschetta is the grilled bread with A topping, doesn’t have to be tomatoes, sometimes it is beans or meat. The chopped tomato and spices they sell premade at the store should probably be called Bruschetta topping.

In the United States, the word is sometimes used to refer to a prepared topping, sold in jars and usually tomato-based, instead of the bread, a sense which is unknown in Italian.

https://en.wikipedia.org/wiki/Bruschetta#Etymology

What you’re asking is one of the glories of living language.

Strictly, bruschetta is an Italian food preparation, with a specific meaning in Italy and the Italian diaspora. But, as is often the case with culture bleeding, the word got adopted and can change in meaning.

So, you run into the colloquial usage of bruschetta to mean that a topping is what turns bread into bruschetta, and thus the topping is the defining part and can be called the same without modifiers like topping being added to the word bruschetta.

With any living language, unless you have a formal version that is regulated, the usage of words are the definitions of them. The only question is degree of consensus, since if enough people agree to a set definition, any irregular usage becomes “wrong” until that changes.

That means it’s fair to say that bruschetta, in English, can mean both the dish once prepared, and the ingredient which finishes the dish.