The simple mathematical model used for the relaxation response only applies to the 14C in the atmosphere and over short periods of time. The 14C behaves chemically and biologically like ordinary CO2. But there are time lags involved and the carbon that is released back into the atmosphere may be depleted in 14C.
If αA > βB in the state diagram above the end result would be that all of the nitrogen in the atmosphere, A, would disappear and end up being transferred to the storage state, C. This result is also likely for γ > β. The 14C that ends in storage also undergoes decay and is transmuted into 14N. This nitrogen could end up being released back into the atmosphere through some chemical or biological decay process that is not included in the model. Some of the processes that affect ordinary CO2 are referred to in the following video.