FWIW, my ISP told me that yes, the 2 day DLM "training" period is indeed valid, but up to 10 days have to be allowed for the connection's MSR (Maximum Stable Rate) to be determined before "faults" can be reported.
First, your ISP has no choice but to repeat what brainwashed BT staff tell them. It does not make the BT statement correct. The BT documentation itself debunks the myth.
Second, in the case of ADSLx, it is true that the 10-day period establishes the MSR and hence the FTR. Nobody has ever disputed that. But there are many cases where there is a clear fault during that period, where an extremely low sync can occur, not just a feasible DLM line adjustment.
In such cases the fault needs to be corrected and the 10 days re-started. Otherwise the MSR and FTR are incorrect and the whole point of the 10-day period is negated. Hah - fat chance! (It does occasionally happen, but I think only with on-the-ball ISPs).
Third, in the case of FTTC, the MSR and FTR may be retained by BT Wholesale in their DLM, for ease of implementation similar to those described in my previous post, but they are totally irrelevant to the Openreach process line management system. The initial stabilisation takes place in the first couple of days, and that's all there is to it. If BT Wholesale continue, for some unkown reason, to want to wait 10 days before setting the MSR/FTR for admin purposes, then they should change the name to something like
Line Assessment Period. Even in the two community threads linked to earlier they still say "stabilisation period". It simply, incontrovertibly. has nothing to do with stabilising anything.

In fact it contributes greatly to the
destabilisation of customers' confidence in BT.
My broadband basic info/help site - www.robertos.me.uk
My domains,website and mail hosting - Tsohost.
Internet connection - Plusnet Value Fibre.
"Where talent is a dwarf, self-esteem is a giant." - Jean-Antoine Petit-Senn.
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