The last two times I've gone in on E, I have noticed that the closer I was to Kam'lanaut, the less accurate Light Blade became. Now, I'm hesitant to make a call on accuracy actually being variable for a few reasons. Firstly, since higher-tier mission fight enemies all have combat skill levels representative of level ~99 mobs only, you'll actually parry and block quite a bit during these fights. If you have Ochain with merits, you're at 100% block rate. It's not like a Delve boss that you use Intervene on, where you immediately know that you've dropped the ACC because before it had capped ACC.
Obviously, I will continue to tinker with this and update accordingly.