Ask HN: Does YC Reserve the Right to Participate in Future Rounds?

On this page, http://ycombinator.com/about.html, it says: "We try to interfere as little as possible in the startups we fund. We don't want board seats, rights to participate in future rounds, vetoes over strategic decisions, or any of the other powers investors sometimes require."

I just pulled up the YC Series AA docs, which includes the following clause in the termsheet under "Investor Rights" and "Right to maintain proportionate ownership":

"Each holder of at least [_________] shares of Preferred will have a right to purchase its pro rata share of any offering of new securities by the Company, subject to customary exceptions. The pro rata share will be based on the ratio of (x) the number of shares of Preferred held by such holder (on an as-converted basis) to (y) the Company’s fully-diluted capitalization (on an as-converted and as-exercised basis). This right will terminate immediately prior to the Company’s initial public offering or five years after the financing."

Is that a reservation of YC's right to participate in future rounds? I don't mean to be accusatory: I'm asking because I'm using what YC does as the gold standard for what an accelerator should do, and I'm wondering whether an accelerator's reservation of rights to participate in future rounds is "standard" behavior.

I'd be very interested to hear the thoughts of those more well-versed in this stuff.