Houses of Soviet construction

In Soviet houses, during the repair you can stumble upon amazing things. For example, there are situations when part of the doorway is made of a wooden beam, which is then plastered and visually looks part of a concrete slab. The same “wooden” solution can sometimes be found at the junction of the plates, when for some reason the gap and the builders knocked it with a tree between them. Perhaps, during the construction of the house, this made some sense, but now such cracks need to be unequivocally concrete.