Well you're certainly getting the speed test well below the estimates, as you said. (I didn't doubt that).
But the stats are something different from speed test results. As I said, they will have the connection speed (sync/line rate), attenuation , noise margin or SNR/SNRM. Those tell us about the technical aspects of your line.
Another useful test, which is a speed test, is the
BT Wholesale Performance Test, (ignore all the red instructions, just click that you've done them), but don't stop at the initial results page. On that, click the Further Diagnostics button near the bottom. Then copy and paste the full contents of the two text boxes of results from the page that gives you

.
The indispensable man or woman passes from the scene, and what happens next is more or less the same thing as was happening before.
My broadband basic info/help site -
www.robertos.me.uk. Domains, site and mail hosting -
Tsohost.
Connection -
Plusnet UnLim Fibre (FTTC). Sync 57676/14040kbps @ 600m. -
BQM