Basically yes. The article source is able to confirm attacks by Orcas on moose have happened.
The only "maybe" part is whether any moose has been fully eaten by any Orca. Occam's razor says yes, but the whole encounter is a rare enough (or just rarely documented!) occurrence not to be widely documented yet.
I don't know if it's rare or incredibly hard to document. How do you attempt to track that? You'd need cameras in the water all over the place, all with an internet connection, and the water would have to be clear enough to see through, and the attack would have to happen right next to the camera, and someone would have to notice it.
I guess the alternative is we put a tracker in a bunch of moose and then dissect a lot of orcas and try to find the trackers.
It just seems like something we're unlikely to know how common it is for a very long time, if ever.
I thought there was an annual migratory path where moose crossed the frozen areas from Alaska to Russia, and as the warming has occured they have to cross more water now, becoming more prone for longer to orcas. Could be wrong, but I seem to remember that from some where
Dolphins are known to be assholes, and Orcas are really big dolphins. That beach dive move is like swerving to hit an animal in the grass/sidewalk on the side of the road.
Orcas are in the dolphin family which is a branch of the whale family, specifically those with teeth rather than baleen. Compare how humans are in the ape family which is a branch of the primate family, specifically those that are less arboreal and lack tails. If we can say humans are primates, we can definitely say that orcas are whales.
Orcas are actually moose. You see there are 2 sexes in the Meese family. The Male have legs and horns and truck around on land, the Women have flippers and swim around the ocean. Moose all have 1 thing in common, it's a fetish for being eaten. The Orcas eat the Moose, consuming their sperm and it gets pushed out towards the egg prior to working it's way out of the esophagus into to the stomach.
I'm yet to see a convincing, authoritative historical source on the "whale killer" factoid. Follow the trail on asesina-ballenas and Basque fishermen and you get nowhere.