ACP Test for Discretionary plus Safe Harbor Match

I hope someone can verify that I understand this correctly.  401(k) plan has 100%-4% enhanced safe harbor match.  They added a discretionary match of 100%-15% for NHCE only in 2019.  Since the discretionary match exceeds 4%, ACP testing applies.  If I test all of the matching contributions together the ACP test fails - a lot of NHCE still didn't participate even with the extra generous match.  However, I believe 1.401(m)-2(a)(5)(iv) allows us to exclude employees who are only receiving the 100%-4% enhanced safe harbor match from the ACP testing.  Since that group to be excluded includes all of the HCE, the ACP testing automatically passes.

Is that correct?  In other words, as long as the HCE are excluded from the discretionary match, ACP is going to be automatically satisfied regardless of the discretionary match formula being used for the NHCE.

What the referenced section says is that you can disregard the safe harbor matching contributions and perform the ACP test on only the discretionary match. If only NHCE received any discretionary match then the test will pass automatically.

100% to 15% match?? Nice.

Thank you!