[quadrangle]

The point is that when someone directly compares 6/8 and 3/4, the implication is that the tactus (the place you feel the primary beat) is supposed to be different.

Of course you can take 3/4 music that happens to use a lot of two-bar structures and play it with the same feel as the same thing notated as 6/8.

But the point of comparing the two is not to highlight that case where the same music could be written either way. The point is to describe how if you take the same 6 8th-notes and give them a 3×2 feel, it's musically different from a 2×3 feel.