EEG/fNIRS connectome source localization

Hi all,

I am getting into brain connectivity from EEG and fNIRS.
Like in this paper Blanco et al.
https://www.sciencedirect.com/science/article/pii/S1877750324002096

it seems to me that sometimes people map the source signal to an atlas similarly to the averaging for MRI atlas, but sometimes they use the signal directly from the sensors, claiming that this is already proxy for known mapping sensors-to-ROI:

so what is the most accepted procedure?