Current Melting of Greenland's Ice Mimicks 1920s-1940s Event, page-2

Sure, Greenland warmed quickly from 1919-1932. Even faster than recent years.
No dispute.

But the whole point of the Box paper is that Greenland was still cooling in the 1970's and 80's, while the Northern Hemisphere (NH) overall was warming, and history shows it is not uncommon for Greenland to lag. The paper discusses how the sulfate aerosols that cooled the rest of the planet from 1940-70 have had a delayed and extended impact in Greenland.

So the paper looks at the current period as just the start of the catch up of Greenland temps to NH temps. It shows that when Greenland catches up it has historically reached warm peaks that are much more warm compared to the mean than is the case for the NH overall.

So they are anticipating much more severe ice loss from Greenland, as Greenland catches up with Northern Hemisphere warming.

Hardly good news or any sort of argument that the planet isn't warming.