Imu really left without checking and he/she didn’t realize Teach and Eris were saved. At this point I think the WG didn’t know Teach was still alive and Shamrock told the Gorosei that Marshall D. Teach is Xebec’s son and a Davy.
Explain this scene and why Saturn told Catarina and Van Auger about the special lineage.
The parallelism between Garling and his son:
Garling found the Davy clan in God Valley
Shamrock learns about Teach as Xebec’s son and a Davy.
I don’t know if the WG and Imu think Teach and Eris are dead in God Valley but it seems Imu didn’t realize imo.
( + I don’t know if this is Shanks and not Shamrock, Oda is a troll sometimes)