No you can scratch it off with those metal base brush sticks that you stick through the openings between your teeth. It’s not perfect but if you do it regularly it helps A LOT. The dentist will have to clean up the trickier parts though (like the inside/back surfaces).
I'm pretty sure studies have been done that show it doesn't have the abrasive power of actual floss, so it's not as good at removing plaque. Fine at removing solids generally, which helps, but actual floss tends to be better.
I legitimately didn't know something like this existed, thank you. is there any reason why one would continue using normal disposable floss rather than a water flosser?
Yes, a water flosser does not help against calculus. But it’s still a nice fresh feeling with water so it’s not a bad thing. But to get rid of calculus you need to physically rub/scratch it off with floss sticks between the teeth.
It shouldn't replace regular flossing, but if it is between no flossing, or only occasionally flossing, and using a water flosser every day, I'd imagine using just the water flosser is still a net positive.
Already commented on another, but my understanding is that water flossing isn't as good at removing plaque as actual floss, since it isn't as directly abrasive. It's great if you wouldn't floss normally otherwise, but migrating from flossing regularly to only water flossing regularly is a downgrade in dental hygiene.
You're correct that it isn't as good of an alternative as flossing but you're meant to do both.
You should floss, preferably with actual floss and not a pick, and then follow that up with water irrigation. You dislodge food and break up the plaque with the floss and flush it out with the water flosser.
I use a charcoal lined floss in a reusable glass container. For whatever reason I could never find a water flosser I liked.
I'd add a copper tongue scraper to the dental hygiene kit. That thing made my general plaque build up significantly less/reduced. Now I somehow feel unclean without it and a toothbrush on the tongue just doesn't even come close.
I've generally had good luck with the Waterpik brand. My last one lasted like 6-7 years before it started to leak, which for a $50-70 product is decent enough for me.