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I'm not sure why you need the simplification. This is a feature (!) of Python, the underlying language of Sage.

sage: (x==1 or x==2)
x == 2


See this stackoverflow question. Basically,

sage: bool(x==1)
False


which makes sense in Sage terms, since we only say an expression is True if we can verify that it is true, and then since the first thing is False, or returns the other thing.