In the Wikipedia 10–20 system (EEG) the electrode positions when plotting are much like the following image (EEG1010.lay) extracted from Fieldtrip, where the midline (T9 -- Cz -- T10) is definitely a straight line.

But in MNE when I plot the standard montage like the following:

import mne

montage = mne.channels.read_montage('standard_1020')
montage.plot()

I end up with this plot (standard_1020) where the (T9 -- Cz -- T10) line is curved down.

Why there's this difference? And there are any implications on topomap visualizations?

Thanks in advance!