Yes he did and it made sense,
50 years ago...
Of course you are correct.
But I personally thought the take away from Iomegaman's observation was that the techniques from 50 years ago can still teach us something, not that we should still be recording and mixing in mono.
Personally, in my time as a musician making records in the past, I recall several times where listening in mono on one speaker allowed us to hear when an arrangement or simple chord inversion could be changed for the better to allow greater depth, clarity , or space.
However, it's very possible I'm just a product of my time and none of this is relevant.
At the end of the day I respect any and all ways that great records are made
Peace.