I think it stole some of the upstream tone/bands to give me a higher noise margin on down stream and now have upstream Interleaving too.
Is that a random guess or are you actually looking at bitloading or something concrete to reach that conclusion?
Band plans are pretty strict. OpenReach uses an of the shelf bandplan with a couple small tweaks.
The same tones/bandplans are used nationwide.
ECI can't just randomly take a bunch of downstream tones and change them to upstream.
There's thousands of sites with ECI and Huawei cabinets on the same PCP. Their bands match (give or take a tone or 2) but don't overlap each other on the downstream/upstream on any tones.
If 1 vendor swapped some of downstream tones for upstream it would cause crosstalk havoc on those tones.
I don't think we've seen a band plan change in VDSL2 for about 7-8 years and it was a small tweaks to stop the 2 vendors overlapping by a couple tones.
See:
VDSL tones in useThe pbparams command on Broadcom chipsets gives the tones in use by the DSLAM.
There's probably an equivalent for Lantiq.