To have an even distance to the formwork at the edge area (and thus to maintain the minimum concrete cover). If the reinforcement were to lie directly against the formwork, that would be bad, wouldn't it?
The distance to the formwork is simply maintained by not placing the reinforcement against the formwork. What else should spacers achieve. The architect's proposal is good. The reinforcement must be protected from rust. It will be. It is iron. It should not occur, but it is also not the end of the world.
We discussed everything again with the structural engineer and recalculated. Fortunately, the thickness of the floor slab is sufficient.
Keep in mind that because the altered floor slab is almost 25% less thick, you also have to pay less for it, as in a floor slab of, for example, 10x10 meters, 7 cm means 7 cubic meters less concrete.