Validation of the hadronic physics in Geant4

Hi all,
I’ve been working on generating neutron simulations following neutrino interactions in ice between, and have been able to successfully produce simulations of neutrons and photons in Geant4 following neutrino interactions. I want to understand is the validity of the simulation.

Having had a look at the G4NDL, the Geant4 manual and also some of the implementation files in Geant4, I was able to understand that essentially for the hadronic simulations, it appears that neutron production following interactions follows a hybrid approach: taking particle propagation via cross sections/path lengths in a given medium, and then selecting a chain of processes for different particles. It is this chain I would like to understand better if possible.

I saw on the G4NDL that there are some probability density functions regarding multiplicities, angular distributions and energies etc of final states (eg neutrons/gammas etc.)

For example:

These come from the Hydrogen-1 capture data for the gammas. Please can you help me to understand where these pdfs come from, and compared to experimental data, how much we can trust these pdfs? If you can assist in any way that would be very helpful.

I am also aware that Geant4 has a Physics Validation TaskForce so I wonder if my question might also be directed there also.

Any help you can provide me is much appreciated, thank you in advance.
Many thanks and best wishes!