It's not that I don't understand.
It's that I don't care that the way they function isn't the way
you think they should.
I have a friend who parses (don't we all

) and I enjoy out-DPSing the DPSs on a big trash pull. Perhaps you think that's inappropriate for a healer, but as I said, I run a Sage, not a "healer." And even the Endwalker trailer emphasizes a Sage doing DPS over heals.
FFXIV offers four classes they label as "HEALERS" and apparently none of them fit your definition of that label. But me, I judge them on what they are, not on the labels people hang on them. Same as I do with people, BTW.
You wanna relabel Sage as a support class instead of a healer? Fine, as long as I still get fast queue pops.