I think what they mean is that trying to guess people's specific opinions outside of "yes" or "no" is actually the problem with how things are worded. Instead of just letting people give simple answers like "I liked it," or "I guessed Peridot's powers," and then maybe asking for people to expand on those answers if you think it's necessary, most of these responses are forcing people to agree with very specific opinions.

Like, for example, when you asked whether we guessed that Steven would aquire floating powers prior to the airing of "Steven Floats," there is no neutral answer at all for people who didn’t. I, personally, just am not the kind of person to theorize about episodes before they air. I find it detrimental to my viewing experience, so I just don't do it. But instead of just being able to answer with a simple "no," I had to agree with one of three opinions that had nothing to do with my reasoning and assumed things of me that weren't true (like that it never occurred to me that he could possibly float, or that I just don't care about his powers at all). And I ended up having to do that for quite a few questions, so a lot of my responses just weren’t really accurate.

I think that using more neutral answers by default leads to less biased, more accurate results than listing a few--sometimes strong--opinions and then giving an other option.

I know that polls are a lot of work and I think a poll gauging the sub's reactions after each week is a great idea! Plus, a lot of people who are finding fault with your poll are doing it in a less than polite way... But not leading the poll takers to certain answers or opinions is probably the most important part of making a poll, so I think it's definitely something to think about when you're making your next one! :)