I believe that is White Fantasy quartzite. There is a granite called White Fantasy, but it does not look like that. With quartzite, it is hard to know whether it is true quartzite, or whether it will behave more like marble in the way of etching and staining. Some quartzites like Taj Mahal are impervious to etching, staining and scratching.

You would need to test it first. Get a sample, and drip some lemon juice or vinegar on it, and see if it etches. If you cannot bring home a sample, try scratching the edge of one of the slabs with a knife. Real quartzite will not scratch or will perhaps have a faint scratch. But marble will scratch easily, as it would as your counter when you drag a plate across it or similar. If it shows itself not to be true quartzite, then it is up to you whether you want to live with a more marble-type of stone.

Here is a pic of White Fantasy granite:

Edited to add: if that OP slab is more of a marble, your stoneyard's recommendation to "seal every 2-3 years" is complete BS. It would need to be sealed minimum once a year, and more like twice a year. Furthermore, sealing protects against staining, but not etching. Between that BS recommendation, and telling you the stone is granite when it isn't, I would find a different stoneyard. This one seems sketch.

I would do your research and understand what you’re getting. It’s highly unlikely that it is granite (no such thing as soft granite, slab yards often misidentify their inventory) but more likely marble. I recommend researching the difference between marble, granite, and quartzite (many marbles are also referred to as soft quartzite and again, no such thing). There are some great stone threads on here tyat explain the difference. If it’s a marble, as I suspect, it may etch, which sealing won’t protect you from. It’s best to get a sample of the slab and test it.

Stone identification resource thread from a geologist