  In these proceedings, we reiterate and extend the discussion of the
Next-to-Leading Order (NLO) QCD analysis of the charged pion Parton
Distribution Function (PDF) obtained within the Fant\^omas4QCD framework. The
goal of the Fant\^omas analysis is to quantify the dependence on the
parametrization form in global QCD analyses, with a first application to the
pion PDFs. We highlight the anti-correlation between the experimentally allowed
gluon and sea distributions in the pion, as made apparent by the sampling over
parametrization forms. This result, for the sea and gluon sector, illustrates
the importance of accounting for epistemic uncertainties in data-driven QCD
analyses. In that regard, we further discuss the meaning of the sampling
uncertainty and why it is key in phenomenological studies of hadron structure.
