I didn't query that
. But on BT Wholesale WBC/WBMC connections over it, the sync is fed from the Openreach system into the BT Wholesale DLM. All that does is set, and use, the IP Profile, in the same way as it sets and uses it on ADSLx.
The BTW one doesn't control the line on FTTC though. The Openreach one does that. With an input from BT Wholesale of the stability option chosen.
Kindness isn't going to cure the world of all its awfulness but it's a good place to begin. Daisy Ridley.
My broadband basic info/help site - www.robertos.me.uk.
Domains, site and mail hosting - Tsohost
Connection - AAISP Home::1 80/20. Sync 65618/13914Kbps @ 600m. BQMs - IPv4