How this is better than ESP8266?
A Cortex-M0 + BLE setup would easily outlast an ESP8266 battery-wise, it would also make more sense on the go (BLE devices can communicate directly with a phone app, without much setup). While an ESP8266 is more general - can connect directly to wifi (more work, and more "stationary").
It's a very different use-case than that of the ESP8266.
I say this, because I have devices doing it in front of me. Maybe not for 'years and years', but certainly efficiently enough for long-term sensor usage.
I guess it really depends on how often you have to transmit - if you have hourly checkins the world looks better than if you have to update something every minute or so.
They're using it to describe a short, relatively large transfer of accumulated data collected while the wifi connection is deactivated, and transferred in a sudden stream when it's turned on.
* Good English documentation * Radio is fully documented - you can make your own wireless protocols * Supported by mBed