You know , it's entirely possible that HE / AP rounds for ISU-152 is an entirely temporary change.
Since it was not actually documented, and still isin't in relics changelog
"Ninjas – Don’t Come Around Here No More
We’ve heard your feedback comments regarding ‘ninja’ updates, and have made a concerted effort to ensure that changes made are reflected in the final patch notes. As a large team with many different people contributing to an update over several weeks, it can be tricky for us to track everything that goes in. This is something that we’re committed to improving, and have heard your concerns on this loud and clear. Ninjas are awesome, but it’s apparent that our passionate community doesn’t want them anywhere near our patch notes. We appreciate your patience with us as we work to streamline this process! You will see our patch notes become better, faster, stronger, and less stealthy over time."
-Cynthia Griffiths
unfortunately the discrepancies in the change logs are more due to poor documentation than unintended implementation. but it is entirely possible its just a temporary stop gap.