I understand this thought for external dependencies, but dependencies also includes internal ones, which I don't see a reason to reduce. Modularity and re-usability of individual pieces of code are a good sign for me.
I assume they mean external dependencies when they say that. I'm not sure what the point of the statement would be if it included internal ones.
Dependency managers like NPM don't differentiate between internal and external dependencies. I assumed that the Svelte devs were referring to this. Vue for example only has internal dependencies, but NPM shows them as any other: https://www.npmjs.com/package/vue?activeTab=dependencies