One detail that caught my eye from your post was this chart:

I was a bit surprised to see the global average WTP being $67k per QALY or ~5x world GDP per capita, while for these individual countries they seem closer to 0.5-2x. 

Eyeballing the chart below from OP's 2021 technical update makes me wonder if that discrepancy is driven by the higher WTP multipliers in LMICs:

But contra my own guess, the authors say

As we’ll discuss in Appendix A, there are empirical and theoretical reasons to think that the exchange rate at which people trade off mortality risks against income gains differs systematically across income levels, with richer people valuing mortality more relative to income.

so I remain confused.