I think I'm the one who's been using this distinction and can't think of any others here who have.
By Orthodox (note the big O) I always mean the Eastern Orthodox communion.
Can one be orthodox without being Orthodox?
I think there are Eastern Orthodox who will say no. But I also think even those who say only Orthodoxy is the Church will concede that there are those outside it who agree with many of its teachings and perhaps could be described as small-o orthodox.
I admit my view, that one can be orthodox but not Orthodox, reflects a more Catholic and even high-church Anglican view, a kind of 'mere orthodoxy', 'mere catholicism' or 'mere apostolicity' shared by Eastern Orthodox, Oriental Orthodox, Assyrians and Catholics.
(Certainly I don't think co-administrator Mor Ephrem, a member of the Malankara Church, is not orthodox!)
And what is this orthodoxy? Fidelity to the teachings in the Bible. The Nicene and Athanasian Creeds (the last isn't used liturgically by Orthodox but I've seen it printed at the beginning of the Russian book of hours, in Slavonic), and the content of the western baptismal creed known as the Apostles': the Trinity, and the divinity of Christ, who is true God and true man. The special place of Our Lady as Mother of God, her intercession and that of the rest of the communion of saints. The all-male apostolic ministry of bishops and their ordained deputies, priests and deacons. And the truth about the Eucharist: that it is the Sacrifice of Christ and is literally the Body, Blood, Soul and Divinity of Christ.
Basic credal orthodoxy as summarized above is what I mean by orthodox, catholic and apostolic.
Can one be Orthodox without being orthodox?
As nonsensical as it sounds, yes - there are born Eastern Orthodox who deny some of this basic orthodoxy. (For example, people who vote for or work for proabortion Presidents. Those who are not prolife but still think they're Orthodox because of their Eastern European heritage.)
Sometimes I use orthodox to describe those classical Protestants who are still thoroughly Christian, reserving catholic and apostolic only for those bodies that have maintained all the points I have summed up above.