You took that from the page titled "Discovery (observation)". Of course it says that discovery requires observation.

Here's a more nuanced view:

Scientific discovery is the process or product of successful scientific inquiry. Objects of discovery can be things, events, processes, causes, and properties as well as theories and hypotheses and their features (their explanatory power, for example).

https://plato.stanford.edu/entries/scientific-discovery/

So it can refer to either the thing itself or to the theory that explains it. Using your definition, theoretical scientists could never "discover" anything.

We say Einstein "discovered" general relativity, even though he was a theoretical physicist, and never physically observed anything first.