Not quite: It's taking advantage of (1+a)(1+b) = 1 + a + b + ab.
And where a and b are both small-ish, ab is really small and can just be ignored.
So it turns the (1+a)(1+b) into 1+a+b. Which is definitely not the same! But it turns out, machine guessing apparently doesn't care much about the difference.
So it turns the (1+a)(1+b) into 1+a+b. Which is definitely not the same! But it turns out, machine guessing apparently doesn't care much about the difference.