Earlier quoted context omitted.
Isn't practically everything you see in a fish market flash frozen anyway? Afaik there's very little fresh fish going around, period. It's all frozen on the boat.
We hope so! Flash freezing kills parasites (Sure, it's not an issue if you cook it thoroughly before consumption, but still)
It depends where you are.
If you are in a Western country, then yes, "sashimi grade fish" equals "frozen".
If you are in Japan, then no.
Its all to do with the understanding of fish and its handling.
In the West its all commoditised, quantity over quality.
In Japan, they have a deeply rooted fish culture, a focus on quality and are obsessive over food hygiene.
So in Japan your sushi won't be pre-frozen, but it will have been meticulously inspected and prepared.
Fun fact, salmon sushi/sashimi is a Western thing. The Japanese don't eat it because the parasite risk in Salmon is so much higher than any other fish.
Personally, having visited Japan a number of times, I will not eat sushi or sashimi outside of Japan any more.