Can't exactly remember what he said but when asked for clarification he admitted he didn't know. He alluded to the fact nitrogen wants to release quickly from the beer and that the process of putting it in is hard. He also said co2 is part of the brewing process, this is true but he failed to mention beers in cans/bottles are mostly dead beers (brewing process is stopped) therefore no co2 remains in the beer. Co2 is then introduced according to Henry's law. The interaction between the gas and the fluid is influenced by the temperature of the fluid/container. Gas escaping from the fluid is easily explained by using fizzy pop. If you open a chilled bottle you get a quick release of co2, open a warm one it overflows. When a keg of beer has the correct gas pressure applied to it, it is considered in equilibrium. This means it is stable. As the tap is opened the gas balances. The head of pressure pushes the beer through the pipes to the tap.
Different gases are absorbed at differing rates. Co2 is absorbed 5 times quicker than Ni. Brewers prefer lagers etc to only contain Co2. Most dispense systems though use a gas mix. The reason for this is the pressure can be higher thus helping with dispense. If pure Co2 is used this will be set at a far lower pressure and will require a pump to help dispense the beer and therefore there are added costs. Nitro beers such as stouts and ales still contain Co2 but the Ni helps form the head. As mentioned gases are absorbed at different rates, this does have an impact on the quality of the beer. If a lager is dispensed using a 60/40 gas mix Co2/Ni, after 4 to 5 days the liquid will start to absorb Ni, this affects the beer. If you ever tasted a lager and it has a metal taste (this used to be caused as well by aluminium kegs coated with an alloy)it is the taste of Ni, Co2 is tasteless.
Another couple of taste issues associated with gas are, the gas bottles running, this can go unnoticed until the flow of beer slows down and starts to fob. Also this can lead to the beer suddenly tasting of cider. If the NRV is missing in the keg coupler gas can interchange between all the kegs connected to the system. The reason for this is when the fluid is in equilibrium the gas actually falls in and out of solution. The other reason is during the Co2 shortages suffered recently pubs started to source gas from other suppliers. Some got gas from farm suppliers. Their beer ended up tasting of shit!
