Jesus’s interaction with the Syrophoenician woman, therefore, reinforces the Jew/nations boundary. The scene may, perhaps, hint at openness to the nations, for Jesus notes that the children must be fed first (πρῶτον), leaving open a possible later gentile mission depicted as feeding dogs.[121] However, this also should not be over-interpreted, for nothing in the imagery suggests the dogs are transformed into children, or that they receive any sort of food typical of children rather than dogs. In fact, the emphasis on the priority of children eating implies nothing transformative about any expected food for the dogs, but rather assumes a typical, ordered hierarchy between the children and their dogs in or around a family home. Therefore, Jesus’s healing of the Syrophoenician woman should not be seen as a watershed moment in Mark’s narrative as Jesus turns toward the nations, but rather as it is depicted in the narrative: an unwanted interruption that surprises Jesus, but results in dogs remaining dogs and eating dog food, and children remaining children and eating their food first
(THE GOSPEL OF MARK WITHIN JUDAISM, READING THE SECOND GOSPEL IN ITS ETHNIC LANDSCAPE, by JOHN R . VAN MAAREN, B.A., p. 256)
Note 121 reads
In this sense, Mark would agree with Matthew, who presents Jesus’s message as directed to Israel during Jesus’s life (Matt 10:5–6), but to the nations after his resurrection (28:19).
(my bold)
Now it becomes clear why even Mark is against Marcion.