Indeed, it’s been known for a long time that when the BBC say “sources close to the Prime Minister” they mean “Dominic Cummings, who is too slippery to put anything on the record”.
The Times, and BBC’s Kuenssberg have had recent success over these tidbits longer than Cummings has been with the PM. He was with Gove for a while.
Yeah, it's a tradition that stretches way back, to the Blair years at the very least - when "King SPAD" was Alastair Campbell, also known as the main inspiration for the character of Malcolm Tucker in "The Thick Of It".