I'm guessing it's because of the fact that the only reason Awe is on Seraph's Embrace and Archangel's Staff is because of the %mana refund passive that they added to tear. Before they added that, the passive on Seraph's Embrace and Archangel's Staff was called Insight, not Awe, and the bonuses stacked before as well, so it's not an interaction they thought should be removed.
It's kind of like Iceborn Gauntlet still creating the slow zone if you have Lich Bane or Trinity Force, and how Stattik Shiv/Rapid Fire Cannon/Warlord's Bloodlust all trigger at the same time when Energized effects are ready, or like how if you have both Luden's Echo and Runic Echoes, you get the mana restore from Runic if the main spell procs against a monster, but the 3 lesser bolts still use Luden's Echo's higher damage if the lesser bolts hit a champion (to my memory).