Is it just me or does A look written wrong?

Like is it supposed to say finding a claim to be false on the grounds that it would be true if it didn't have false consequences/ consequences that are false.

Cause I immediately thought this was the right answer but then hesitated cause it read weird and tried eleimanintong all the other answers 1st.

Was anyone else confused by the "not otherwise"

I've never seen that used in writing ever, and it really confused me what it meant.