Actually, I've found Lu Xun defending exactly that in the part VIII of that essay.
This is absolutely not an "idiosyncratic interpretation".
Imperfect translation: "Expressing one's own thoughts with this was impossible, the number of characters being far too small. In short, it was as if a prisoner had been given a little space, but limited in such a way that he could walk, stand, sit or lie down, without the possibility of jumping out of the cage installed for him."
This is absolutely not an "idiosyncratic interpretation".
Imperfect translation: "Expressing one's own thoughts with this was impossible, the number of characters being far too small. In short, it was as if a prisoner had been given a little space, but limited in such a way that he could walk, stand, sit or lie down, without the possibility of jumping out of the cage installed for him."