Thanks for investigating the matter, but I don't agree that the passage supports the sayadaw's view. Since Sāriputta's brother, Revata, is only seven years old, the Dhp-a narrative concerns his going forth as a sāmaṇera, not his full acceptance as a bhikkhu. As such it has no bearing on the Vinaya issue of obtaining parental permission if one wishes to obtain upasampadā.
When Sāriputta says, mama mātāpitaro micchādiṭṭhikā, kiṃ tehi āpucchitehi ("my mother and father are holders of wrong view, so why bother taking leave of them?"), as I see it he is not abbrogating the Vinaya obligation to obtain parental permission (for it doesn't apply here), nor introducing any amendment to the Vinaya (something that he as a disciple would have no authority to do), but merely announcing his intention to dispense with conventional courtesies.