No I kinda see what the theory is, though it doesn't seem to fit the technique as I understand arb. The idea being to buy XYZ in one market and simultaneously sell it in another market because there is a price discrepancy between the two markets, in other words, the price is wrong in one market, doesn't really matter which one, when price corrects in whichever market, ie XYZ has the same price, then both positions are closed and the original difference is profit. This would however not seem to be the case since the difference in price between the spreadbet quote is not a discrepency, but intentional and therefore will not correct. That would be how I'd see it anyways.