That is an orthogonal concern.

Versus

That is an entirely different concern.

The second is more approachable but requires an adverb to have the same meaning, and adverbs are also discouraged. I think orthogonal is fine.

Also it does not communicate the precise meaning. "Orthogonal" fits when concerns may be related, but they're independent from one another, so you can discuss them separately.

Well, regardless of the adverb, you would need a modifier. Avoiding these technical considerations was part of Orwell's point I think.

So I guess we could nitpick over "entirely" and "basically" just as easily. Maybe he should have just singled out the engineers and other pedants.

Perpendicular is a weird word. And also harder to say, at least for foreigners.

I tend to use "mutually independent" instead of "orthogonal" when talking with non-tech people.