How are people having huge mem oc on their rtx cards?

Seeing people post their rtx cards with 1000, 1100, +1200 memory clock ocs, I'm wondering how that's safe when there's no VRM temp sensors on the majority of these cards? Definitely not on my evga 3070. I'd love to clock it to that but I'm not trying to melt my memory and burn out the card. Even a +400 mem clock feels concerningly burning to the touch. Can anyone shed light on this