Right, so I just did some testing on the "new and improved" HEAP which now bumps 150mm and 152mm up beyond the 32mm threshold point to penetrate tier 8+ BB bow and tier 8-9 BB deck (Iowa is 38mm however)
This was tested at approximately 13.6km on a bow-forward Izumo using a fully upgraded Cleveland. Important thing to note here is that the shell caliber, and therefore the HE penetration* is shared with the Belfast and Kutuzov, two very special CLs with smoke and 6" guns that will see tier 8-9 BBs.
*HE penetration is caliber/6-1 (so 150mm is (150/25-1)=24mm HE pen), the exception bein