Let's say the middle price of a 1175 strike should be 2.5, and the middle price of a 1200 strike should be 7.5 (as an example). These numbers would be arrived at using a standard options pricer, where the required inputs would be ATM implied vol, 25 delta and 10 delta butterfly (in vol) and 25 delta and 10 delta risk reversal (in vol).
The "fair value" of this spread is 5. If HC spots that the spread can be traded at 6, and sells it there, then he's taking advantage of some small inefficiency.
However, he seems to cross two bid/ask to trade, so the calculation would be more like -
1175 put, fair value 2.5, price 1/3 (mid 2.0)
1200 put, fair value 7.5, price 7/9 (mid 8.0)
So you can see that the 1175 K is slightly offered, whilst the 1200 K is slightly bid. HC would then sell 7 and buy 3, for a net credit of 4, when fair value is actually 5. Due to crossing spread twice, he ends up dealing WORSE than fair value.
So if HC can trade these spreads AS spreads (i.e. only cross one bid/ask), and can accurately calculate their theoretical mid using Black Scholes and the associated interpolated implied vol, then there might be some microscopic edge to be extracted over time. However, commissions will probably negate this approach.
So.. I'm still not seeing a valid strategy here. It's worth noting that the markets have been extremely accommodating since he started trading.. we'll need to see a bit of a shakeout to the downside to see how he handles a volatile market.