If there are differential perceived benefits in social prestige/power from transitioning based on direction, this is consistent with there being only one factor (sexism) conditional on direction but also consistent with there being unconditional benefits plus the pushmi-pullu effect of swapping testosterone & other androgens for estrogen etc in which the net effect for the mtf is indeterminate. I am willing to take their word on transitioning being good for them, which accounts for the first factor, I prefer experimentally demonstrated effects from powerful mind-altering hormones to unprovable spooks like institutional sexism, and so the hormone model seems to me to fit much better.