There's something wrong there! I don't think you are reporting back correctly.
Quite honestly, at present I'm not bothered by the different scenarios. There is no real significant diff between them.
Are you saying that your router only shows one figure for both Down & Up against NM & Attn? There should be separate figures for Down & Up.
Or are you saying that your router does show separate figures for Down & Up, but they just happen to be equal?
A typical router would say:
Downstream Upstream
Data Rate (kbps) 12403 1020
Noise Margin (dB) 5.5 12.3
Attenuation (dB) 30.6 16.4
1999: Freeserve 48K Dial-Up => 2005: Wanadoo 1 Meg BB => 2007: Orange 2 Meg BB => 2008: Orange 8 Meg LLU => 2010: Orange 16 Meg LLU => 2011: Orange 19 Meg WBC