Rally points and completion credit?

I got all the way to near the end of Midnight on legendary solo, but I’m stuck against 7-8 knights who seem to be experts at killing me in various bs ways, inbetween grenade spam and melee’d-you-before-even-exiting-teleport. And the game won’t give me a checkpoint even after there’s only the cannon one left, so I usually have to do it all over again.
tl;dr Light rifle/suppressor vs 3-4 knights at once = bad bad bad

I know that directly loading from that save file/checkpoint, obviously, will get me the credit for solo legendary completion.

But since that checkpoint is bad (see above), would I still get the credit if I just restarted the mission from the last rally point instead of my own checkpoint?

Or rephrased, does the game remember partial-up-to-rally-point difficulty completion, or must you do it beginning-to-end loading off of player checkpoints only?