Maybe Harald told Loki that Loki was the one who needed to eat it?
Harald prophesized Loki killing him to begin with, so, I wonder how much other stuff Harald foresaw.
The reason Loki didn't tell anyone Harald was betrayed by the WG is clear: Elbaph loves Harald to pieces, they would 1000% declare war on the WG if they found out what happened, and be crushed.
Loki covered up the WG involvement in Harald's death, and took the blame, to keep Elbaph from invading Marijoa/declaring war on the WG. To protect Elbaph.
Now that the God's Knights/Imu are attacking directly, though, there's NO point in keeping it under wraps, so, Elbaph will likely declare war against the WG very soon. Which fits into their ties with Usopp/Sogeking, who Luffy instructed to shoot down the WG Flag in Enies Lobby, a declaration of war against the WG.