Ajahn Tong has deviated from the main point of Mahasi Sayadaw's meditation technique?

I have heard the claim that Ajahn Tong deviated from the main point of Mahasi Sayadaw's meditation technique and he taught it as a concentration technique. I don't understand how that could be. Yuttadhammo Bhikkhu isn't teaching concentration meditation and he is Ajahn Tong's student. Does anyone know why anyone would make this claim? As I understand, Ajahn Tong was pretty strict about not practicing just concentration meditation.