I think they mean that while those teams are all working individually, Yoshida himself (and other senior development staff) are always busy managing/producing the next content from all teams. Regardless of who works on the nitty gritty, the same people have to work on implementing it into the game, checking up on what they're doing, and presenting it to the players. The actual artists may not be busy with 1.19, but Yoshida and the rest of the people who would be able to actually post those artists' work for us to see are busy with 1.19.