I've been shocked by how quietly Medium went about this change. It seems like almost every commenter here was unaware of it, and many of them, like you, had been sharing the standard links without realizing they were unopenable. I spent a few weeks doing it myself and I was pretty frustrated and embarassed when I realized.
Of all the shifts made in my time since joining Medium, it definitely strikes me as one with the hugest implications. I'm truly not sure I'd be hear without those free reads I'd been given. I've noticed a stark dip in the external viewers I've been getting since the change was implemented.
Thanks for reading, Colby!