ᐅ Using granite palisades for raised garden beds with a dimpled membrane?

Hello, as a tribute to our late son, we want to plant a tree for him in the garden. It is a flowering cherry tree.

The tree is intended to be the visual centerpiece of the garden.

Therefore, I have built a raised bed from granite palisades.

These are 75cm (30 inches) high and will ultimately protrude 50cm (20 inches) above ground level. Nearby there will be a wildflower meadow; here the palisades are 50cm (20 inches) high and will stick out 30cm (12 inches) from the ground.

I applied 10-15cm (4-6 inches) of frost protection material underneath, compacted it, and then poured the concrete. The palisades are each set in concrete to about 25cm (10 inches) and 20cm (8 inches) respectively.

Now everything should slowly be refilled with soil.

Does the dimpled membrane (often recommended) have any purpose other than preventing soil from falling through small gaps? Granite is a stone that generally does not absorb moisture.

In this case, I would place the dimples facing inward so that the membrane lies flat against the stones.