Is it safe to use non-sashimi grade fish to make gravlax?
IMO.

Gravlax is not technically "raw" it is cooked (cured) with salt and sugar, both of which have been used to preserve food for eons.

In any case, use as fresh as possible fish you can find from a reputable fish monger.


Yes; as long as you properly cure the fish and properly store the fish in the fridge.
Was it safe before ? The "traditional" gravlax, was fermented salmon buried in sand. don't know, there are still Scandinavian people, so I assume it did have such an impact. 
They so it the same way we do it, with salt and sugar, and vacuum pack it. (I cannot find the ingredients list for it online); maybe they add a little bit of preservative, but I would be surprised.