Is backfilling the wall with clay soil sensible?

Hello,
we need to secure the fill against our neighbor on our hillside property and want to do this using a concrete block wall (which will be plastered afterwards). Now, our property mainly consists of clay soil, of which unfortunately we have more than enough on our property.

We are now considering backfilling the wall (height is 1 meter) to 80 centimeters and placing a perforated drainage pipe (leading to the sewer) on top, then covering it with topsoil and grass. For the protection of the wall, of course, a dimpled membrane will be placed between the wall and the soil. On the internet, it is always stated that backfilling is best done with gravel. But for me, the question arises: where does the rainwater go if the gravel only drains the water and does not retain it? From our point of view, it would then accumulate at the base of the back of the wall, which is of course not ideal.

Attached is also a picture... of course, some wall is still missing there, but the right side will be backfilled by us...

With "our" solution using clay soil (which is so hard and dry and hardly absorbs any water) and topsoil, at least the topsoil can store the water, and any excess can then be drained away through the drainage pipe. What do you think???

Thank you very much in advance for your help :-)

If the wall is plastered, then paint the back side with bitumen so that the plaster holds. There is also primer that is waterproof from the front but don't ask me which one.

I would lay the drainage in the gravel bed and then connect it to the drainage system.

We also filled up to 1m with clay, the rest 20cm with topsoil substrate.

Have you omitted a strip foundation or is it just not visible in the picture? The absence of a foundation would currently worry me more than the drainage over the clay soil.

Thanks first of all for your answers.
: actually, only the part that is exposed should be plastered. We also considered bitumen on the backfill side, but we would only put a dimpled membrane on it.
: the foundation is of course present (between 45 and 65 cm) and there is also compacted gravel underneath. We also put plenty of steel into the wall.

Nevertheless, we are unsure whether, because of "our" construction with clay and topsoil, we might eventually get moisture problems in the wall!?