I think that this is a historical view that was taken by previous governments that didn't want to offend Putin. Putin is very offended by the word “Magnitsky”. In the past, different foreign ministers didn't want to offend Putin when we were in the world of appeasement. We're not in a world of appeasement anymore. Nobody wants to appease Putin. We should always call it Magnitsky both because it's the right thing to do—it's now a verb pretty much around the world—and it also has the added benefit of upsetting Putin every time he hears the word.
On March 30th, 2023. See this statement in context.