Instant coffee is actually freeze dried and yes should dissolve completely, while grinds will never just disappear in the water.

But then there's that.

A couple of weeks ago we went abroad and asked a friend of mine to watch our apartment because I had flowers that needed pollinating. In exchange he could stay at the apartment. Since he's a Ukrainian refugee who has to share a room with a questionable dude he gladly took me up on that offer.

Now, we are coffee snobs, my husband's youtube history is full of James Hoffmann. So we have a manual espresso press at home, a hand filter, a french press, two moka pots, and a senseo pad machine (for guests; our filter machine just broke).

When we came home, we found a can of instant coffee. Jacobs, to be precise, and everything in Ukrainian. Dude brought his instant coffee to our coffee infested place. Knowing that he has been here for a while and drinks a lot of coffee, I asked him how did this can last him so long. He got it imported. He freaking imported Ukrainian Jacobs instant coffee into Germany.

And then we start reading the can's text a bit more profoundly. It is a mix of normal instant coffee, i.e. freeze dried, with a bit of finely ground coffee mixed in. It does not dissolve completely. It takes ages for the grind to settle to the bottom. I don't know who thought this was a good idea. I don't know what the purpose is supposed to be. But they advertise it heavily on the package.

Also, I tried a cup and it does taste like shit but to each their own.

Tldr: instant coffee usually is freeze dried coffee that will dissolve completely but there are some unholy products designed by questionable people that contain real grind coffee for no reason.