I wouldn't trust anything from the Mediatek chipset.
The fact you can play with UPBO, override the DSLAM, tweak various power settings, etc, shows me they have a very loose attitude to following ITU standards.
The way they calculate the attainable is way off how Broadcoms do. They over inflated the attainable with G.INP the same way they do with interleaving. There's no delay with G.INP, not on Bearer 0 anyway.
Only when my line was on Fastpath was the attainable anywhere near accurate.
My attainable on my DSL-AC68U was some 30Mb+ over inflated at times.