I agree. I didn't notice that rule but it makes me hesitant to sign up. If I do, I'll just offer my OTP and an & ship that's in the tagset that doesn't turn me off as a writer (or just the & version of my OTP). But the recip doesn't deserve receiving 300 halfhearted words of the & ship because I lucked out of writing what I was really into writing. The exchange interested me because (at least it seemed to me) it'd be an exchange where people were matched on what they really wanted, genfic or shipfic. But apparently the exchange doesn't have that quality and so I'm hesitant to sign up.