You don't NEED to fill the 12 ram slots. My personal 1U has an Epyc 9124 and only 4 of the 12 ram slots filled. I figured, ram will only get cheaper with time so I can fill the remaining 8 slots in the future. Turns out I was wrong, but regardless, the server runs fine on 4 sticks.

Haha the 'need' is a joke need. Like I need to upgrade my 9654s to the 9755 I have sitting in a box.