I think that’s because of the last phrase in this provision in the DMA (article 13.4 in https://eur-lex.europa.eu/legal-content/EN/TXT/?uri=uriserv%...):

“The gatekeeper shall not engage in any behaviour that undermines effective compliance with the obligations of Articles 5, 6 and 7 regardless of whether that behaviour is of a contractual, commercial or technical nature, or of any other nature, or consists in the use of behavioural techniques or interface design.”