It looks like the DLM is capping the line rate.
That is what Id expect it to do. Well in actual fact I would first expect it to increase error protection and then cap.
The HH5B is far from the best router to test with as it doesnt give you any g.inp/retransmission values, so you dont know what its doing on the error protection side. Need to get a modem/router such as a HG612/Billion/Zyxel to do some proper testing.
That's exactly what I've done. Want some stats? Here you go!
Stats recorded 02 Feb 2016 15:41:10
DSLAM/MSAN type: BDCM:0xa48c / v0xa48c
Modem/router firmware: AnnexA version - A2pv6F039g1.d24m
DSL mode: VDSL2 Profile 17a
Status: Showtime
Uptime: 2 hours 35 min 45 sec
Resyncs: 0 (since 02 Feb 2016 13:59:08)
Downstream Upstream
Line attenuation (dB): 25.8 0.0
Signal attenuation (dB): Not monitored
Connection speed (kbps): 35000 8493
SNR margin (dB): 9.7 6.7
Power (dBm): 12.0 5.8
Interleave depth: 8 2
INP: 54.00 53.00
G.INP: Enabled
RSCorr/RS (%): 0.0001 0.0010
RSUnCorr/RS (%): 0.0000 0.0000
ES/hour: 0 0