Question about the scaling factor in ROOT’s weighted Poisson log-likelihood (WLS fit)

Thanks! @StephanH I’m referring to the same implementation discussed in this earlier ROOT Forum thread:

https://root-forum.cern.ch/t/weighted-log-likelihood-estimation-for-low-statistics-binned-histogram/58191

@moneta Lorenzo’s reply there includes the relevant source code and a detailed explanation of how the weighted likelihood is implemented. My current question is a follow-up to that discussion: I understand how ROOT evaluates the expression numerically, but I’m trying to understand the statistical motivation for the scaling factor.