G.fast is less likely to be subject to crosstalk due to the much lower take up. I also believe G.fast is vectored?
As for VDSL, my poorer line:
VDSL Port Details Upstream Downstream
Line Rate: 20.202 Mbps 54.953 Mbps
Actual Net Data Rate: 20.000 Mbps 54.864 Mbps
Trellis Coding: ON ON
SNR Margin: 6.1 dB 6.1 dB
Actual Delay: 0 ms 0 ms
Transmit Power: 5.5 dBm 13.7 dBm
Receive Power: -10.2 dBm 0.8 dBm
Actual INP: 0.0 symbols 0.0 symbols
Total Attenuation: 15.7 dB 12.7 dB
Attainable Net Data Rate: 20.606 Mbps 54.884 Mbps
============================================================================
VDSL Band Status U0 U1 U2 U3 D1 D2 D3
Line Attenuation(dB): 4.5 15.4 24.6 N/A 8.3 18.8 30.2
Signal Attenuation(dB): 4.2 15.2 24.5 N/A 10.2 18.6 30.1
SNR Margin(dB): 10.1 6.4 6.0 N/A 6.1 6.1 6.1
Transmit Power(dBm):- 6.6 -28.8 5.3 N/A 10.8 7.2 7.6
============================================================================
Increasing to 56.140 Mbps with a different modem.
My better line:
Bearer: 0, Upstream rate = 20000 Kbps, Downstream rate = 62249 Kbps
Down Up
SNR (dB): 6.4 7.6
Attn(dB): 13.9 0.0
Pwr(dBm): 13.7 5.3
Increasing to 66.14Mbit with a different modem.
So while I absolutely agree you should be pushing for this to be looked into, this is the reality of what crosstalk can do. Both my lines used to be capable of full sync a few years ago. In fact my good line used to sync at 100/30 when I was on Digital Region (council VDSL that went bankrupt) with zero crosstalk.