You're referring to the PoE challenge mode right? The "weekly bounty" where you earn 30000/90000 points. Doing those will give you guaranteed max light rewards, right?
Kings Fall normal is up to 320 light, hard mode is up to 330 light. I don't know if PoE provides guaranteed level or another "up to" situation.
The "up to" stuff has got to stop. I'd rather go back to VoG/Crota where you only had the RNG of getting the drop, but at least you knew the item would reach max level after putting in the XP and materials.
I sort of miss the days of having to scrounge up ascendant shards and energies to rank my stuff.