I do it in fifteen seconds at most, stuffing it without any consideration just keeping two corners in one hand, then matching them with two cover's corners and gently shaking.
Also genuinely baffled about the article, but to be honest, not the first time that I hear someone hating the procedure and describing some problem that I don't understand.
Maybe 30s here, but I'm not claiming to be the fastest; I'm wondering if body length is a factor. As a somewhat tall person (189cm) in my 50s I never had any issues changing doona covers.
Had a much shorter girlfriend at one point who simply said "that's not fair" when she saw me do it.
The arm reach factor - I can stretch a queen size duvet tight, holding corner to corner. (AU Queen = 210cm X 210cm).
For fitting, standing up I'll just feed one corner of the doona into the cover and find a corner to pinch, then the same for the other side - then open wide, and shake it out.
It so easy, which is why I was also baffled to see an article about making this easier to do.
(It's a small thing and it doesn't matter at all, but the ex seemed to notice it.)
Also genuinely baffled about the article, but to be honest, not the first time that I hear someone hating the procedure and describing some problem that I don't understand.