Yes, this is what I thought probably happened, as well. The "us" referred to the support agencies, and they likely were no longer able to change canonical URLs (surprising they were allowed to do so to begin with).
Sadly, it's not archived anywhere I could find, but it did mention that you could send them a CSV file of up to 50 URLs to update the canonical links for.
That doesn't contradict anything the agent said. I believe you that they could previously set canonical links. But it's highly likely that upper management changed that policy (I'm surprised they allowed it to begin with).
IMO, it's not too surprising that they tried to be a bit more writer friendly initially (to attract more quality writers and larger publications). I guess it no longer fit with their new business objectives, which is why they quietly removed it this fall.
Sadly, it's not archived anywhere I could find, but it did mention that you could send them a CSV file of up to 50 URLs to update the canonical links for.