ᐅ Corner bricks without drainage

Hello,
My landscaper wants to install 50cm x 30m (20 inch x 98 feet) L-shaped retaining stones on the slope. Although we have heavy clay soil, he intends to place them only on gravel. We have no way to drain the accumulating water (the garden slopes down toward the planned retaining stones), so it can only infiltrate into the ground. My question: Won't these stones create a retaining wall that holds back water? The company El specifies that a drainage system should be installed inside the L-shape to prevent water from collecting behind it.
Wouldn't it be better to choose a more permeable solution?
What alternatives are there?

There is a drainage system every 50cm (20 inches)...

No. There is no drainage on the slope. The stones are placed precisely against each other, and the joints are intended to be compacted.

Google image search for "drainage retaining wall" shows many pictures illustrating the correct way to do it: a drainage wall and drain pipe. However, the water still needs to be directed somewhere, for example into a soakaway, sump, or sewer.

With a garden wall, it’s not a big problem to leave this out – building the foundation on 30cm (12 inches) of gravel and backfilling with gravel also provides some drainage.

But it seems that I will end up with a damp corner on my clay floor, since water will accumulate behind the stone. Or am I wrong?

fragg schrieb:
a drainage is installed every 50cm (20 inches)...

I agree. As long as the joints between the L-shaped blocks are not sealed watertight somehow, water will still pass through there.