https://en.wikipedia.org/wiki/ANT_(network)
I believe that's what the author was referring to when describing it as failed, but yes, this could've been worded better.
Contrast with BLE where you would have to make a connection to each device. The overhead of connecting and disconnecting, in addition to being power-prohibitive, takes too long. Some manufacturers have workarounds to enable use of their BLE products in a group fitness environment, but they are pretty much lacking.
It'll be interesting to see how the problem is solved if indeed ANT+ does go away.
Also the connection process isn't power-prohibitive for BLE, and it doesn't have to take a long time. It's just that most Bluetooth software stacks suck balls. Basically only Apple's is good.
As I recall BLE only supports hosts connecting to 7 peripherals simultaneously which is a bit rubbish, but if you're a gym with some custom ANT+ receiver you can definitely get a custom BLE receiver that can connect to more devices (assuming someone makes such a thing).
I don't know how difficult it would be to connect, grab a bunch of data and disconnect from 24 BLE devices in a one-second period, which is pretty much what you'd need to be an effective workaround for ANT+. In a competitive environment, data from each device changes very rapidly.