I can’t answer this without more information. I would need your export string from the addon.
I think you might be confusing simulation with gear optimization. When you do BiB, it doesn’t actually simulate your gear. It uses an algorithm that was based on simulations to predict how powerful each gear combination will be. It is impossible to simulate every combination of items you have in your bag.
Our gear ranking algorithm is still in the process of being updated for 8.2 because we have to run millions of simulations and then process the data. We will have an update soon with some new rankings and then will continue to refine them through the first week of the new season/raid.
For the time being, you could use the simulator to check out specific items:
In general the Highborne Compendium is good at its item level.