Thanks Doreen, true, I was referring to that Harvard/Willet bias for seeing positive "plant based" results from an observational study of self reported food frequency questions.
While you could also say the bigger story is that women who ate "higher protein" , about 23% protein or almost 100 grams, ate less, weighed less, and aged healthier based on 11 tests, both physical and cognitive. Versus the women who ate less protein, about 13% or only 58 grams. The baseline diet and health status was 1984 vs 2014/16. Only 7.6% of nurses (who are educated, know health care, etc) were considered healthy 30 years later!
But the numbers pulled out of this huge WHI database appear to support the concept that Protein Leverage works well for older women. (they were age 50-79 in 1984) [ See Prof Raubenheimer and Simpson recent study on "Weight Gain during the menopausal transition "]. Also 12-13% protein is the current US consumption that has likely contributed to the obesity seen now.

This is what the "higher protein" cohort was able to do over 30 years…eat less, weigh less, age healthier. To me, that seems clearer than plant protein being "better" than the other two proteins.