Can a safe harbor plan use shifting / borrowing from ADP to pass ACP

[oberwolfach]

Hello there everyone, we have a safe harbor 401k that allows employee after-tax contributions, so I am running some calculations on what the 2024 test results for our plan would look like under various scenarios. I know that in general, if the ADP test passes with room to spare but the ACP test fails then one can shift / borrow from the ADP test to the ACP test to help pass the ACP test. However, how does this work, if at all, in the case of a safe harbor 401k, since it ordinarily automatically passes the ADP test? Would this tactic not be allowed (and hence constitute a significant disadvantage of being a safe harbor 401k), or would it be allowed to calculate what the ADP test would show and shift / borrow based on those numbers should the ACP test fail? I tried looking around but haven't found an answer since it's kind of a corner case.