I wouldn't call that normal, more of a failure to measure or account for the counter top. As for whether or not to leave it, that's really up to you and whether you notice it and it bothers you. (It would bother me personally).

Depending on how the island is constructed, it may be possible for the contractor to cut down or plane the extra 1/2 inch off to make it even with the rest of your kitchen.

Agree 100% with @Stephanie Nocito.

Base cabinets are constructed at 34 1/2”H as a standard. That puts the finished counter height right at 36” above the finished floor, when it is installed at the finished floor height.

If your old cabinets were sitting on the subfloor, and the new ones are sitting at he finished floor height, it was your old ones that were non standard.

... it’s normal amd isn’t a big deal true or false?

False and true. It's not normal, but, unless you are really short, 1/2" isn't a big deal. Since an island is free-standing, I doubt anyone else will ever notice it, and you'll probably forget about it, after you start using the kitchen.

ETA, I have a work-table/island in my kitchen. It's a custom height of 34", for my comfort when rolling dough, etc. No one has ever commented that it's 2" shorter than the perimeter counters--even guests who might be helping with last-minute prep.

Set a level between your perimeter cabinets and your island. If they're level you have no complaint.