You’re correct, unsure why this got a downvote. Think of how distilled water feels weirdly slick in the mouth, almost a bit like glycerin. Soluble minerals are chemically grippy on the grounds and between the tastebuds. Their absence leads to underextracted coffee.

Depends on the minerals. It absolutely matters, in a way apparent to most folks’ palates when drinking a quality cup. At the high end, or for finicky industrial testing, or for things like comparative tastings in different locations, there is even engineered coffee brewing water with controlled chemistry for peak performance.