You don't slice individual portions of meat before serving. If I order a pork chop or a ribeye at a restaurant, I'd be horrified if it came pre-sliced.
And for something like an entire roast, you want to slice shortly before serving so it doesn't get too cold.
Just account for carry-over cooking and cook it less initially, or sous vide.
Many times I've ordered a large cut of meat, like a porter house or a tomahawk (usually intended to be shared with the table), they have came pre sliced. I'm pretty sure even Peter Luger's will pre slice it for you even for an individual.
There are many, many instances where you do.
The context of the article is obvious. It's about things like steaks and chops served in an American/European style.
Saying that they can technically be served sliced is to miss the point entirely. This isn't about stir-fry or salads.