But she did that intentionally.
Yes, I know. In "Before Dishonor" she also walks in "intentionally".
He means that she died intentionally, not that she merely decided to go there intentionally. Endgame Janeway went to the cube fully intending to be assimilated and to die there. Before Dishonor Janeway went to the cube with the intention of seeing for herself what was up and walking away from it alive and well. The first was a sacrifice the second was an accident.