Unfortunately, this is not the case; you can make it say really whatever you want:
Yes, by completely changing the meaning of the words.
For example, you can set up a different number system which would count something like:
1,2,3,5,...
in which case 2+2=5.
You can change the "+" function to be something other than addition, or change the meaning of "2" or "=".
Or you can just ignore all that and output the line "2+2=5" like what a lot of people there did.
That doesn't change what we have meant when we say 2+2=5.
And again, THIS IS NOT SPECIAL TO MATH!
You can do the exact same in English.
For example, I can arbitratily decide that your statement:
"Unfortunately, this is not the case;"
to instead mean something like:
"Yes, you are absolutely correct."
It doesn't actually mean you said that.
Or more to the topic of a flat Earth, you can simply switch the meaning of flat and round, so a flat Earth is one which approximates a globe, while a round Earth is one which has no curvature.
That doesn't mean Earth is actually flat, it just means you are pretending flat means something else.