It's both really. Supporting SBD while also hurting the price of STEEM. It may be above the current price but a huge sell order slightly above market is still going to weigh on the price. I don't think that is really questionable.
That said, it is and always has been the advertised plan of 'steemit' to sell a large amount (approximately 25% of the total holdings of that account; approximately 20 million USD worth!) of STEEM, which indeed redistributes it to buyers, so no one should be surprised by any of this really. I might disagree about strategy as to how fast or when to sell, but that is not based on anything objective at all. Steemit's strategy here is certainly defensible.
The original post was mostly a reasonable analysis, pretty balanced in pointing out the redistribution effect, and original work on a topic of obvious interest that no one else has published afaik.
(I deleted my own comment)