They cover that in the first paragraph of the article. Pulsars need to be spinning fast because physics. This thing is too slow.

On Wednesday, researchers announced the discovery of a new astronomical enigma. The new object, GPM J1839–10, behaves a bit like a pulsar, sending out regular bursts of radio energy. But the physics that drives pulsars means that they’d stop emitting if they slowed down too much, and almost every pulsar we know of blinks at least once per minute.

GPM J1839–10 takes 22 minutes between pulses. We have no idea what kind of physics or what kind of objects can power that.