Does this make it any better?
…I don't think so?
Since with the addition of this statement:
Another bit is that typed statement would have always been true within the affected area, altering the whole timeline within the area of effect.
Then how would anyone be able to tell if anything is going on with the typewriter? Those outside the bubble AoE would probably think it causes hallucinations, the people inside the AoE would think it doesn't do anything besides type.
Trouble with fate-altering objects like these is that the whole "but how would you break it" continuity is really hard to write up convincingly. We, uh, actually get an object like this at least once a month, and it rarely does well.