Can I cut in shortening ahead of time?

I agree with both posts above. Yes, refrigerate. It's necessary to keep the shortening cold. But the layering and steaming sound more relevant to puff pastry than biscuits (although the word "steam" still bothers me. Biscuits rely on both shortening and leavening for flakiness and height-and. a light hand with the dough.

Shortening steams?

Shortening contributes to flakiness but biscuits rely on leavening for rise.

The only real variable you have to watch out for here is that your shortening doesn't get warm. So cut it into your dry ingredients and immediately refrigerate. Otherwise it will blend with the flour, and your biscuits will not be flakey. It should be fine this way until the next day as long as you wait to add the liquid on the day you plan to finish the dough off.

Biscuits are flakey because the fat is not blended into the flour. When the dough is rolled out, it creates pockets of fat that steam when cooked and that makes flakey biscuits.