Yes frozen strawberries are just as healthy as fresh strawberries are.
Although frozen strawberries are usually less tasty than fresh strawberries are but they still are good frozen.
Freezing strawberries can extend the life of the strawberries so they don't mold or go bad sooner than you can use them.
I grow strawberries in my garden and will freeze the strawberries and keep them for making ice cream, strawberry cakes or just eat them when I thaw them out.
I keep strawberries for a few years when frozen before I use them up.
I grow lots of strawberries and freeze them.
The strawberries contain the same nutrition and vitamins when frozen as they do when fresh.