I'm just making a guess here, so please forgive me if I'm mistaken. That said: my guess is that what the Orthodox monk has in mind is the great similarity between the Christian teachings on the 'passions' and overcoming them through cultivating the 'virtues' to the Buddhist teaching on the 'poisons' & their 'antidotes' and the role of meditation in bringing the two together.
I'm guessing, too, that the more an Orthodox Christian moves from verbal prayer into a wordless and imageless prayer of the heart the more similar what is being done is to what I understand to be the practice of Theravada and Zen Buddhist meditation (but not Tibetans Buddhist!).
I could be quite wrong, of course, in thinking that the Philokalia Fathers see the Jesus prayer as moving from repetition of words into a sort of silent waiting on the Lord, but that is how I understand it. This sort of silent waiting (not on the Lord Jesus, of course) is exactly what Zen and Theravada Buddhist meditation is working toward as well. It's just a state of calm, aware openness into which both one's sins and guidance about how to overcome them as well as guidance on how to deal with daily troubles (and occasionally a great sense of relief) bubbles up. Christians would no doubt view the source of this bubbling as the Holy Spirit or Jesus or the voice of God. Zen and Theravada teachers I've spoken to are more reluctant to assign a specific origin to it. (Since some Zen teachers are at the same time Roman Catholic priests or nuns--or even Jewish rabbis--I don't think we need to panic about Buddhism as long as we hold firmly to our own Christian faith.)
Christian monks and nuns of all traditions who have had contact with monks and nuns who practice Buddhist meditation often remark on the great similarity of what they all do. So I wouldn't be overly worried if one Orthodox monk said what he is quoted as saying even if it isn't the sort of comment you'd expect from your priest.