They're researching the behaviour of real neurons by making computational models, rather than creating a "neural network" model for AI purposes, so the definition of "single neuron" they're using is meant to reflect the original meaning of the term.
The gist seems to be that more distant synapses can't initiate an action potential, or firing of the neuron, but can prime the neuron to fire in reaction to synapses closer to the cell body. This means that outer synapses can provide 'context', e.g. indicate that prior steps in a sequence have been recognised, while inner synapses can cause firing if the context is fulfilled, i.e. context + necessary condition (recognition of the most recent step in the sequence) = action potential.
It's not computationally surprising, but it is a specific cellular mechanism.