Sunak not only did not mitigate risk by hedging his bet with Piers Morgan he didn't - and this is the 'gambling' element for a hedge funder - he made no attempt to profit from the aforesaid risk mitigation. This profiteering comes via the margins i.e., changes in movements in the derivatives used to mitigate risk and usually expressed in terms of interest rates, f/x spot rates, yields, etc, etc. 'Gambling' because it seeks to (a) forecast the future, (b) profit from it (not just mitigate it) and (c) for all of the sophisticated means of assessing market trends and measuring market volatility, there still remains the risk of (i) not making a gain and (ii) even making a loss. This is because the future is uncertain.
All Sunak did was make a stupid bet and compounded it by claiming he was 'taken by surprise' and in any case, that he 'never bet' which he obviously once did as a professional paid to do so, see above.