He is supporting the government. He is also picking his battles. I think he is definitely holding back rather than being seen as haranguing the government when they need to focus on other things. It speaks volumes that tory supporting press are giving Johnson a bad angle on this and his response to Starmer. He's getting comments on record now, because he knows he can come back to them later when they are on record. Calling out the detail, disparity, inaccuracy etc is what is needed rather than just letting them get away with it, or going full on attack dog mode.